Edgar Filing: TRIANGLE PHARMACEUTICALS INC

Filed Pursuant to
Rule 424(b)(1)
Registration No 333-62730

PROSPECTUS

2,000,000 SHARES

TRIANGLE PHARMACEUTICALS, INC.

COMMON STOCK
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This prospectus relates to the resale of 2,000,000 shares of
common stock held by the selling stockholders identified in this prospectus.

Our common stock is traded on the Nasdaq National Market under the
symbol "VIRS." On July 9, 2001, the last reported sale price for the common
stock was $4.10 per share.

INVESTING IN OUR COMMON STOCK INVOLVES A HIGH DEGREE OF RISK. SEE "RISK
FACTORS" BEGINNING ON PAGE 3 TO READ ABOUT SOME IMPORTANT RISKS YOU SHOULD
CONSIDER BEFORE BUYING ANY SHARES OF OUR COMMON STOCK.

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NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED THESE SECURITIES, OR PASSED UPON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

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The date of this prospectus is July 11, 2001

TABLE OF CONTENTS

PAGE

I. OUR BUSINESS..........................................................3

II. RISK FACTORS..........................................................3

III. FORWARD-LOOKING STATEMENTS...........................................21

IV. USE OF PROCEEDS......................................................22

V. SELLING STOCKHOLDERS.................................................22

VI. PLAN OF DISTRIBUTION.................................................23

VII. LEGAL MATTERS........................................................25

VIII. EXPERTS..............................................................25

IX. WHERE YOU CAN FIND MORE INFORMATION..................................25

X. INFORMATION INCORPORATED BY REFERENCE................................25

You should rely only on the information in this prospectus or
information we have referred to in this prospectus. We have not authorized
anyone to provide you with information that is different. This prospectus may
only be used where it is legal to sell these securities. This prospectus is
not an offer to sell, or a solicitation of an offer to buy, in any state
where the offer or sale is prohibited. The information in this prospectus is
accurate on the date of this prospectus and may become obsolete later.
Neither the delivery of this prospectus, nor any sale made under this
prospectus will, under any circumstances, imply that the information in this
prospectus is correct as of any date after the date of this prospectus.

I. OUR BUSINESS

We develop new drug candidates primarily in the antiviral area, with a
particular focus on therapies for HIV, including AIDS, and the hepatitis B
virus. We have an existing portfolio of six licensed drug candidates in clinical
trials and several drug candidates that are in a pre-clinical stage or for which
we have an option to acquire a license. Members of our senior management team,
prior to joining Triangle, played instrumental roles in developing and
commercializing several leading antiviral therapies. Our goal is to capitalize
on our management team's expertise, as well as on advances in virology and
immunology, to identify, develop and commercialize new drug candidates that can
be used alone or in combination to treat serious diseases.

Triangle was incorporated in Delaware in July 1995. Our principal
executive offices are located at 4 University Place, 4611 University Drive,
Durham, North Carolina 27707, and our telephone number is (919) 493-5980.

II. RISK FACTORS

IN ADDITION TO THE OTHER INFORMATION IN THIS PROSPECTUS, YOU SHOULD
CAREFULLY CONSIDER THE FOLLOWING RISKS BEFORE MAKING AN INVESTMENT DECISION.
THE OCCURRENCE OF ANY OF THE EVENTS OR CIRCUMSTANCES DESCRIBED IN THIS
SECTION COULD IMPAIR OUR BUSINESS OR FINANCIAL CONDITION, THE TRADING PRICE
OF OUR COMMON STOCK COULD DECLINE, AND YOU MAY LOSE ALL OR PART OF YOUR
INVESTMENT.

ALL OF OUR DRUG CANDIDATES ARE IN DEVELOPMENT AND WE MAY NEVER SUCCESSFULLY
COMMERCIALIZE THEM.

Some of our drug candidates are at an early stage of development and
all of our drug candidates will require expensive and lengthy testing and
regulatory clearances. The regulatory authorities have not approved any of
our drug candidates. We do not expect any of our drug candidates to be
commercially available until at least the year 2002. There are many reasons
that we may fail in our efforts to develop our drug candidates, including
that:

- our drug candidates may be ineffective, toxic or may not receive
regulatory clearances,

- our drug candidates may be too expensive to manufacture or market or
may not achieve broad market acceptance,

- third parties may hold proprietary rights that preclude us from
developing or marketing our drug candidates, or

- third parties may market equivalent or superior products.

The success of our business depends on our ability to successfully
develop and market our drug candidates.

WE HAVE INCURRED LOSSES SINCE INCEPTION AND MAY NEVER ACHIEVE PROFITABILITY.

We formed Triangle in July 1995 and have incurred losses since our
inception. At March 31, 2001, our accumulated deficit was $353.8 million. Our
historical costs relate primarily to the acquisition and development of our
drug candidates and selling, general and administrative costs. We have not
generated any revenue from the sale of our drug candidates to date, and do
not expect to do so until at least the year 2002. In addition, we expect
annual losses to continue over the next several years as a result of our drug
development and commercialization efforts. To become profitable, we must
successfully develop and obtain regulatory approval for our drug candidates
and effectively manufacture, market and sell any products we develop. We may
never generate significant revenue or achieve profitable operations.

IF WE NEED ADDITIONAL FUNDS AND ARE UNABLE TO RAISE THEM, WE WILL HAVE TO
CURTAIL OR CEASE OPERATIONS.

Our drug development programs and our efforts to commercialize our drug
candidates require substantial working capital, including expenses for:

- preclinical testing,

- chemical synthetic scale-up,

- manufacture of drug substance for clinical trials,

- toxicology studies,

- clinical trials of drug candidates,

- sales and marketing,

- payments to our licensors, and

- potential commercial launch of our drug candidates.

Our future working capital needs will depend on many factors, including:

- the progress and magnitude of our drug development programs,

- the scope and results of preclinical testing and clinical trials,

- the cost, timing and outcome of regulatory reviews,

- the costs under current and future license and option agreements for
our drug candidates, including the costs of obtaining and enforcing
patent protection for our drug candidates,

- the costs of acquiring any additional drug candidates,

- the rate of technological advances by us and other companies,

- the commercial potential of our drug candidates,

- the magnitude of our administrative and legal expenses,

- the costs of establishing sales and marketing functions, and

- the costs of establishing third party arrangements for manufacturing.

We have incurred negative cash flow from operations since we
incorporated Triangle and do not expect to generate positive cash flow from
our operations for at least the next several years. We will need additional
future financings to fund our operations. We cannot assure you that available
sources of funds will be sufficient to meet our future needs. In addition, we
cannot assure you that we will receive the contingent development milestone
payments under our strategic alliance with Abbott Laboratories, the Abbott
Alliance. We may not be able to obtain adequate financing to fund our
operations, and any additional financing we obtain may be on terms that are
not favorable to us. In addition, any future financings could substantially
dilute our stockholders. If adequate funds are not available, we will be
required to delay, reduce or eliminate one or more of our drug development
programs, to enter into new collaborative arrangements or to modify the
Abbott Alliance on terms that are not favorable to us. These collaborative
arrangements or modifications could result in the transfer of valuable rights
to third parties. In addition, we may acquire technologies and drug
candidates that would increase our working capital requirements.

To facilitate our ability to raise additional equity capital, on
November 1, 2000, we entered into a firm underwritten equity facility, the
Facility, with Ramius Securities, LLC, and Ramius Capital Group, LLC, under
which we may be able to issue and sell up to $100.0 million of our common
stock over a three-year period. We have filed a registration statement with
the Securities and Exchange Commission for the sale of up to $24.0 million of
our common stock under this Facility. There are conditions and limitations on
Ramius Securities' obligation to sell shares under the underwriting agreement
and Ramius Capital's obligation to purchase shares under the purchase
agreement. In particular, Ramius Securities' and Ramius Capital's obligations
are subject to share price and trading volume limitations which could reduce
the number of shares of common stock they are obligated to sell or purchase,
as the case may be, regardless of the number of shares of common stock we
request to be sold. In some circumstances, such as an average trading price
of less than $4.00 per share, they will have no obligation to sell or
purchase our common stock, even if we request them to do so. In addition, we
may elect not to sell shares of common stock if we believe that market
conditions are unfavorable.

BECAUSE WE MAY NOT SUCCESSFULLY COMPLETE CLINICAL TRIALS REQUIRED FOR
COMMERCIALIZATION OF OUR DRUG CANDIDATES, OUR BUSINESS MAY NEVER ACHIEVE
PROFITABILITY.

To obtain regulatory approvals needed for the sale of our drug
candidates, we must demonstrate through preclinical testing and clinical
trials that each drug candidate is safe and effective. The clinical trial
process is complex and uncertain and the regulatory environment varies widely
from country to country. Positive results from preclinical testing and early
clinical trials do not ensure positive results in pivotal clinical trials.
Many companies in our industry have suffered significant setbacks in pivotal
clinical trials, even after promising results in earlier trials. Any of our
drug candidates may produce undesirable side effects in humans. These side
effects could cause us or regulatory authorities to interrupt, delay or halt
clinical trials of a drug candidate, as occurred with mozenavir dimesylate,
or could result in regulatory authorities refusing to approve the drug
candidate for any and all targeted indications. In April 2000, the South
African Medicines Control Council terminated the enrollment in one of our
phase III clinical studies, study FTC-302, for our drug candidate Coviracil
and the Food and Drug Administration, the FDA, issued a clinical hold on the
study.

We were conducting study FTC-302 under a U.S. Investigational New Drug
Application at sites in South Africa. The FDA indicated that study FTC-302
may not be adequate to provide pivotal data in support of a New Drug
Application. In February 2001, the FDA notified us that the study would
remain on clinical hold even though the study had been completed. Discussions
with the South African Medicines Control Council and FDA are continuing;
however, our planned submission of an U.S. New Drug Application for Coviracil
may be significantly delayed. We, the FDA, or foreign regulatory authorities
may suspend or terminate clinical trials at any time if we or they believe
the trial participants face unacceptable health risks.

CLINICAL TRIALS MAY TAKE LONGER TO COMPLETE AND COST MORE THAN WE EXPECT
WHICH WOULD ADVERSELY AFFECT OUR ABILITY TO COMMERCIALIZE DRUG CANDIDATES AND
ACHIEVE PROFITABILITY.

Clinical trials are lengthy and expensive. They require adequate supplies
of drug substance and sufficient patient enrollment. Patient enrollment is a
function of many factors, including:

- the size of the patient population,

- the nature of the protocol,

- the proximity of patients to clinical sites, and

- the eligibility criteria for the clinical trial.

Delays in patient enrollment can result in increased costs and longer
development times. Even if we successfully complete clinical trials, we may
not be able to file any required regulatory submissions in a timely manner
and we may not receive regulatory approval for the drug candidate. In
addition, if the FDA or foreign regulatory authorities require additional
clinical trials we could face increased costs and significant development
delays, as occurred with Coactinon and which may occur with Coviracil. In
December 1999, the FDA advised us that they would require additional phase
III studies to support a New Drug Application submission for Coactinon. In
July 2000, we presented data to the FDA from a completed phase II study,
MKC-202, showing that a lower dose of 500 mg twice-a-day, compared to the
previous dose of 750 mg twice-a-day, provided similar antiviral activity and
an enhanced tolerability profile in patients taking Coactinon. Based on the
new data, in July 2000, the FDA advised that enrolling an additional 280
patients into an ongoing phase III study, MKC-401, at the lower dose of 500
mg twice-a-day would generate sufficient data for filing of a New Drug
Application if the results were positive. In August 2000, we announced our
decision to continue the development of Coactinon. We completed the
enrollment of the additional 280 patients into study MKC-401 in April 2001.

Changes in regulatory policy or new regulations could also result in
delays or rejections of our applications for approval of our drug candidates.
The FDA has notified us that three of our drug candidates for the treatment
of HIV, Coviracil, Coactinon and amdoxovir, qualify for designation as "fast
track" products under provisions of the Food and Drug Administration
Modernization Act of 1997. The fast track provisions are designed to expedite
the review of new drugs intended to treat serious or life-threatening
conditions and

essentially codified the criteria previously established by the FDA for
accelerated approval. These drug candidates may not, however, continue to
qualify for expedited review and our other drug candidates may fail to
qualify for fast track development or expedited review. Even though some of
our drug candidates have qualified for expedited review, the FDA may not
approve them at all or any sooner than other drug candidates that do not
qualify for expedited review.

IF WE OR OUR LICENSORS ARE NOT ABLE TO OBTAIN AND MAINTAIN ADEQUATE PATENT
PROTECTION FOR OUR DRUG CANDIDATES, WE MAY BE UNABLE TO COMMERCIALIZE OUR
DRUG CANDIDATES OR TO PREVENT OTHER COMPANIES FROM USING OUR TECHNOLOGY IN
COMPETITIVE PRODUCTS.

Our success will depend on our ability and the ability of our licensors
to obtain and maintain patents and proprietary rights for our drug candidates
and to avoid infringing the proprietary rights of others, both in the United
States and in foreign countries. We have no patents in our own name and we
have a small number of patent applications of our own pending. One of our
patent applications is a joint application with co-inventors from another
institution. We have licensed, or have an option to license, patents, patent
applications and other proprietary rights from third parties for each of our
drug candidates. If we breach our licenses we may lose rights to important
technology and drug candidates.

Our patent position on some of our drug candidates, like that of many
pharmaceutical companies, is uncertain and involves complex legal and factual
questions for which important legal principles are unresolved. We may not
develop or obtain rights to products or processes that are patentable. Even if
we do obtain patents, they may not adequately protect the technology we own or
have licensed. In addition, others may challenge, seek to invalidate,
infringe or circumvent any patents we own or license. If they
do so successfully, rights we receive under those patents may not provide
competitive advantages to us. Further, the manufacture, use or sale of our
products or processes may infringe the patent rights of others.

Several pharmaceutical and biotechnology companies, universities and
research institutions have filed patent applications or received patents that
cover our technologies or technologies similar to ours. Others have filed
patent applications and received patents that conflict with patents or patent
applications we own or have licensed, either by claiming the same methods or
compounds or by claiming methods or compounds that could dominate those owned
by or licensed to us. In addition, we may not be aware of all patents or
patent applications that may impact our ability to make, use or sell any of
our drug candidates. For example, United States patent applications are
confidential while pending in the Patent and Trademark Office, and patent
applications filed in foreign countries are often first published six months
or more after filing. Any conflicts resulting from third party patent
applications and patents could significantly reduce the coverage of our
patents and limit our ability to obtain meaningful patent protection. If
other companies obtain patents with conflicting claims, we may be required to
obtain licenses to these patents or to develop or obtain alternative
technology. We may not be able to obtain any license on acceptable terms or
at all. Any failure to obtain licenses could delay or prevent us from
pursuing the development or commercialization of our drug candidates, which
would adversely affect our ability to achieve profitability.

There are significant risks regarding the patent rights of two of our
licensed drug candidates. We may not be able to commercialize Coviracil or
amdoxovir due to patent rights held by third parties other than our
licensors. Third parties have filed numerous patent applications and have
received numerous issued patents in the United States and many foreign

countries that relate to these drug candidates and their use alone or in
combination to treat HIV and hepatitis B. As a result, our patent position
regarding the use of Coviracil and amdoxovir to treat HIV and/or hepatitis B
is highly uncertain and involves numerous complex legal and factual questions
that are unknown or unresolved. If any of these questions is resolved in a
manner that is not favorable to us, we would not have the right to
commercialize Coviracil and/or amdoxovir in the absence of a license from one
or more third parties, which may not be available on acceptable terms or at
all. Even if any of these questions is resolved in our favor, we may still
attempt to obtain licenses from one or more third parties to reduce the risks
of challenges to our patent positions. These licenses may not be available on
acceptable terms or at all. Our inability to commercialize either of these
drug candidates would adversely affect our ability to achieve profitability.

COVIRACIL (EMTRICITABINE)

Coviracil, a purified form of FTC, belongs to the same general class of
nucleosides as lamivudine. In the United States, the FDA has approved
lamivudine for the treatment of hepatitis B and for use in combination with
zidovudine, also known as AZT, for the treatment of HIV. Regulatory
authorities have approved lamivudine for the treatment of hepatitis B and for
use in combination with other nucleoside analogues for the treatment of HIV
in a number of other countries. GlaxoSmithKline plc, Glaxo, currently sells
lamivudine for the treatment of HIV and hepatitis B under a license agreement
with Shire Pharmaceuticals Group, plc, formerly BioChem Pharma Inc. We
obtained rights to Coviracil under a license from Emory University. In 1990
and 1991, Emory filed in the United States and then in numerous foreign
countries patent applications with claims to compositions of matter and
methods to treat HIV and hepatitis B with Coviracil. In 1991, Yale University
filed in the United States patent applications on FTC, including
emtricitabine and its use to treat hepatitis B, and subsequently licensed its
rights under those patent applications to Emory. Our license arrangement with
Emory includes all rights to Coviracil and its uses claimed in the Yale
patent applications.

HIV. Emory received a United States patent in 1993 covering a method to
treat HIV with Coviracil. Emory has also received United States and European
patents containing composition of matter claims that cover Coviracil. Shire
Pharmaceuticals filed a patent application in the United States in 1989 and
received a patent in 1991 covering a group of nucleosides in the same general
class as Coviracil, but which did not include Coviracil. Shire
Pharmaceuticals filed foreign patent applications in 1990, which expanded on
its 1989 United States patent application to include FTC among a large class
of nucleosides. The foreign patent applications are pending in many countries
and patents have been issued in a number of countries with claims directed to
FTC that may cover Coviracil and its use to treat HIV. In addition, Shire
Pharmaceuticals filed a United States patent application in 1991 specifically
directed to Coviracil. Shire Pharmaceuticals has received two patents in the
United States based on this patent application, one directed to Coviracil and
the other directed to a method for treating viral diseases with Coviracil.
The Patent and Trademark Office has determined that there are conflicts
between both Shire Pharmaceuticals patents and patent applications filed by
Emory because they have overlapping claims to the same technology. The Patent
and Trademark Office is conducting two adversarial proceedings,
interferences, to determine whether Shire Pharmaceuticals or Emory is
entitled to the patent claims in dispute regarding Shire Pharmaceuticals' two
issued patents. Emory may not prevail in the adversarial proceedings, and the
proceedings may also delay the decision of the

Patent and Trademark Office regarding Emory's patent application. Shire
Pharmaceuticals also filed patent applications in many foreign countries
based on its 1991 United States patent application and has received patents
in some of these countries. Shire Pharmaceuticals may have additional patent
applications pending in the United States.

In the United States, the first to invent a technology is entitled to
patent protection on that technology. For patent applications filed prior to
January 1, 1996, United States patent law provides that a party who invented
a technology outside the United States is deemed to have invented the
technology on the earlier of the date it introduced the invention in the
United States or the date it filed its patent application. In a filing with
the Securities and Exchange Commission, Shire Pharmaceuticals stated that
prior to January 1, 1996, it conducted substantially all of its research
activities outside the United States. Shire Pharmaceuticals also stated that
it considered this to be a disadvantage in obtaining United States patents
based on patent applications filed before January 1, 1996 as compared to
companies that mainly conducted research in the United States. We do not know
whether Emory or Shire Pharmaceuticals was the first to invent the technology
claimed in their respective United States patent applications or patents. We
also do not know whether Shire Pharmaceuticals invented the technology
disclosed in its patent applications in the United States or introduced that
technology in the United States before the date of its patent applications.

In foreign countries, the first party to file a patent application on a
technology, not the first to invent the technology, is entitled to patent
protection on that technology. We believe that Emory filed patent
applications disclosing Coviracil as a useful anti-HIV agent in many foreign
countries before Shire Pharmaceuticals filed its foreign patent applications
on that technology. However, Shire Pharmaceuticals has received patents in
several foreign countries. In addition, Shire Pharmaceuticals has filed
patent applications on Coviracil and its uses in countries in which Emory did
not file patent applications. Emory has opposed or otherwise challenged
patent claims on Coviracil granted to Shire Pharmaceuticals in Australia and
Europe. Emory may not initiate patent opposition proceedings in any other
countries or be successful in any foreign proceeding attempting to prevent
the issuance of, revoke or limit the scope of patents issued to Shire
Pharmaceuticals. Shire Pharmaceuticals has opposed patent claims on Coviracil
granted to Emory in Europe, Japan, Australia and South Korea. Shire
Pharmaceuticals may make additional challenges to Emory patents or patent
applications, which Emory may not succeed in defending. Our sales, if any, of
Coviracil for the treatment of HIV may be held to infringe United States and
foreign patent rights of Shire Pharmaceuticals. Under the patent laws of most
countries, a product can be found to infringe a third party patent either if
the third party patent expressly covers the product or method of treatment
using the product, or if the third party patent covers subject matter that is
substantially equivalent in nature to the product or method, even if the
patent does not expressly cover the product or method. If any governmental
authority determined that the sale of Coviracil for the treatment of HIV
infringes a Shire Pharmaceuticals patent, we would not have the right to
make, use or sell Coviracil for the treatment of HIV in that country in the
absence of a license from Shire Pharmaceuticals. We may be unable to obtain a
license from Shire Pharmaceuticals on acceptable terms or at all.

HEPATITIS B. Burroughs Wellcome Co. filed patent applications in March
1991 and May 1991 in Great Britain on a method to treat hepatitis B with FTC
and

purified forms of FTC, that include emtricitabine. Burroughs Wellcome filed
similar patent applications in other countries, including the United States.
Glaxo subsequently acquired Burroughs Wellcome's rights under those patent
applications. Those patent applications were filed in foreign countries prior
to the date Emory filed its patent application on the use of emtricitabine to
treat hepatitis B. Burroughs Wellcome's foreign patent applications,
therefore, have priority over those filed by Emory. In July 1996, Emory
instituted litigation against Glaxo in the United States District Court to
obtain ownership of the patent applications filed by Burroughs Wellcome,
alleging that Burroughs Wellcome converted and misappropriated Emory's
invention and property and that an Emory employee is the inventor or a
co-inventor of the subject matter covered by the Burroughs Wellcome patent
applications. In May 1999, Emory and Glaxo settled the litigation, and we
became the exclusive licensee of the United States and all foreign patent
applications and patents filed by Burroughs Wellcome on the use of
emtricitabine to treat hepatitis B. Under the license and settlement
agreements, Emory and we were also given access to development and clinical
data and drug substance held by Glaxo relating to emtricitabine.

Shire Pharmaceuticals filed a patent application in May 1991 in Great
Britain also directed to a method to treat hepatitis B with FTC. Shire
Pharmaceuticals filed similar patent applications in other countries. In
January 1996, Shire Pharmaceuticals received a patent in the United States,
which included a claim to treat hepatitis B with emtricitabine. The Patent
and Trademark Office has determined that there is a conflict between the
Shire Pharmaceuticals patent and patent applications filed by Yale and Emory.
The Patent and Trademark Office is conducting an adversarial proceeding, an
interference, to determine which party is entitled to the patent claims in
dispute. Yale licensed all of its rights relating to FTC, including
emtricitabine, and its uses claimed in this patent application to Emory,
which subsequently licensed these rights to us. Neither Emory nor Yale may
prevail in the adversarial proceeding, and the proceeding may delay the
decision of the Patent and Trademark Office regarding Yale's and Emory's
patent applications. In addition, the Patent and Trademark Office has
recently added the U.S. patent application filed by Burroughs Wellcome to
this interference. Emory may not pursue or succeed in these proceedings. We
will not be able to sell emtricitabine for the treatment of hepatitis B in
the United States unless a United States court or administrative body
determines that the Shire Pharmaceuticals patent is invalid or unless we
obtain a license from Shire Pharmaceuticals. We may be unable to obtain a
license on acceptable terms or at all. In July 1991, Shire Pharmaceuticals
received a United States patent on the use of lamivudine to treat hepatitis B
and has corresponding patent applications pending or issued in foreign
countries. If the Patent and Trademark Office determines that the use of
emtricitabine to treat hepatitis B is not substantially different from the
use of lamivudine to treat hepatitis B, a court could hold that the use of
emtricitabine to treat hepatitis B infringes these Shire Pharmaceuticals
lamivudine patents.

In addition, Shire Pharmaceuticals has filed patent applications and
received patents in the United States and foreign countries on manufacturing
methods relating to a class of nucleosides that includes emtricitabine. If we
use a manufacturing method that is covered by any of Shire Pharmaceuticals'
patents, we will not be able to manufacture emtricitabine without a license
from Shire Pharmaceuticals. We may not be able to obtain a license on
acceptable terms or at all.

AMDOXOVIR (FORMERLY KNOWN AS DAPD)

We obtained our rights to amdoxovir under a license from Emory and the
University of Georgia Research Foundation, Inc., University of Georgia. Our
rights to amdoxovir include a number of issued United States patents that cover:

- composition of matter,

- a method for the synthesis of amdoxovir,

- methods for the use of amdoxovir alone or in combination with
several other agents for the treatment of hepatitis B, and

- a method to treat HIV with amdoxovir.

We also have rights to several foreign patents and patent applications
that cover methods for the use of amdoxovir alone or in combination with
other anti-hepatitis B agents for the treatment of hepatitis B. Additional
foreign patent applications are pending which contain claims for the use of
amdoxovir to treat HIV. Emory and the University of Georgia filed patent
applications claiming these inventions in the United States in 1990 and 1992.

Shire Pharmaceuticals filed a patent application in the United States
in 1988 on a group of nucleosides in the same general class as amdoxovir and
their use to treat HIV, and has filed corresponding patent applications in
foreign countries. The Patent and Trademark Office issued a patent to Shire
Pharmaceuticals in 1993 covering a class of nucleosides that includes
amdoxovir and its use to treat HIV. Corresponding patents have been issued to
Shire Pharmaceuticals in many foreign countries. Emory has filed an
opposition to patent claims granted to Shire Pharmaceuticals by the European
Patent Office based, in part, on Emory's assertion that Shire
Pharmaceuticals' patent does not disclose how to make amdoxovir. In a patent
opposition hearing held at the European Patent Office on March 4, 1999, the
Opposition Division ruled that the Shire Pharmaceuticals European patent
covering amdoxovir is valid. Emory has appealed this decision to the European
Patent Office Technical Board of Appeal. If the Technical Board of Appeal
affirms the decision of the Opposition Division, or if we or Emory do not
pursue the appeal, we would not be able to sell amdoxovir in Europe without a
license from Shire Pharmaceuticals, which may not be available on acceptable
terms or at all. Shire Pharmaceuticals has opposed patent claims granted to
Emory on both amdoxovir and DXG, the parent drug into which amdoxovir is
converted in the body, in the Australian Patent Office.

In a decision dated November 8, 2000, the Australian Patent Office held
that Emory's patent claims directed to amdoxovir are not patentable over an
earlier Shire Pharmaceuticals patent. Emory has appealed this decision of the
Australian Patent Office to the Australian Federal Court. If Emory, the
University of Georgia or we are unsuccessful in the appeal, then we will not
be able to sell amdoxovir in Australia without a license from Shire
Pharmaceuticals, which may not be available on acceptable terms or at all.
Shire Pharmaceuticals' opposition to Emory's patent claims on DXG in
Australia is ongoing. If Emory, the University of Georgia or we do not
challenge, or are not successful in any challenge to, Shire Pharmaceuticals'
issued patents, pending patent applications, or patents that may issue

from its applications, we will not be able to manufacture, use or sell
amdoxovir in the United States and any foreign countries in which Shire
Pharmaceuticals receives a patent without a license from Shire
Pharmaceuticals. We may not be able to obtain a license from Shire
Pharmaceuticals on acceptable terms or at all.

IMMUNOSTIMULATORY SEQUENCE PRODUCT CANDIDATES

In March 2000, we entered into a licensing and collaborative agreement
with Dynavax Technologies Corporation to develop immunostimulatory
polynucleotide sequence product candidates for the prevention and/or
treatment of serious viral diseases, which became effective in April 2000.
Immunostimulatory sequences are polynucleotides which stimulate the immune
system, and could potentially be used in combination with our small molecule
product candidates to increase the body's ability to defend against viral
infection. Immunostimulatory sequences can be stabilized for use through
internal linkages that do not occur in nature, including phosphorothioate
linkages.

There are a number of companies which have patent applications and
issued patents, both in the United States and in other countries, that cover
immunostimulatory sequences and their uses. Coley Pharmaceuticals, Inc. has
filed several patent applications in this area and has in addition
exclusively licensed a number of patent applications on this subject from the
University of Iowa and Isis Pharmaceuticals, Inc. A number of these patent
applications have been issued. A number of companies have also filed patent
applications and have or are expected to receive patents on a number of
polynucleotides and methods for their use and manufacture. These patents, if
granted, could prevent us from making, using or selling any immunostimulatory
sequence that is covered by a patent issued to a third party unless we obtain
a license from that party which may not be available on acceptable terms or
at all.

With respect to any of our drug candidates, litigation, patent
opposition and adversarial proceedings, including the currently pending
proceedings, could result in substantial costs to us. The costs of the
currently pending proceedings are significant and may increase significantly
during the next several years. We anticipate that additional litigation
and/or proceedings will be necessary or may be initiated to enforce any
patents we own or are significant and license, or to determine the scope,
validity and enforceability of other parties' proprietary rights and the
priority of an invention. Any of these activities could result in substantial
costs and/or delays to us. The outcome of any of these proceedings may
significantly affect our rights to develop and commercialize drug candidates
and technology.

United States patents carry a presumption of validity and generally can
be invalidated only through clear and convincing evidence. As indicated
above, the Patent and Trademark Office is conducting three adversarial
proceedings in connection with the emtricitabine technology. We cannot assure
you that a court or administrative body would hold our licensed patents valid
or would find an alleged infringer to be infringing. Further, the license and
option agreements with Emory, the University of Georgia, The Regents of the
University of California, The DuPont Pharmaceuticals Company, Mitsubishi
Tokyo Pharmaceuticals, Inc. (formerly, Mitsubishi Chemical Corporation) and
Dynavax provide that each of these licensors is primarily responsible for any
patent prosecution activities, such as litigation, patent conflict
proceeding, patent opposition or other actions, for the technology licensed
to us. These agreements also provide that we generally must reimburse these
licensors for the costs they incur in performing these activities. Similarly,

Yale and the University of Georgia, the licensors of clevudine to Bukwang
Pharm. Ind. Co., Ltd., are primarily responsible for patent prosecution
activities with respect to clevudine at our expense. As a result, we
generally do not have the ability to institute or determine the conduct of
any patent proceedings unless our licensors elect not to institute or to
abandon the proceedings. If our licensors elect to institute and prosecute
patent proceedings, our rights will depend in part on the manner in which
these licensors conduct the proceedings. In any proceedings they elect to
initiate and maintain, these licensors may not vigorously pursue or defend or
may decide to settle on terms that are unfavorable to us. An adverse outcome
of these proceedings could subject us to significant liabilities to third
parties, require disputed rights to be licensed from third parties or require
us to cease using technology, any of which could adversely affect our
business. Moreover, the mere uncertainty resulting from the initiation and
continuation of any technology related litigation or adversarial proceeding
could adversely affect our business pending resolution of the disputed
matters.

BECAUSE WE MAY NOT BE ABLE TO MAINTAIN THE CONFIDENTIALITY OF OUR TRADE SECRETS
AND KNOW-HOW, WE MAY LOSE A COMPETITIVE ADVANTAGE.

We also rely on unpatented trade secrets and know-how to maintain our
competitive position, which we seek to protect, in part, by confidentiality
agreements with employees, consultants and others. These parties may breach
or terminate these agreements, and we may not have adequate remedies for any
breach. Our trade secrets may also be independently discovered by
competitors. We rely on technologies to which we do not have exclusive rights
or which may not be patentable or proprietary and may be available to
competitors. We have filed applications for, but have not obtained, trademark
registrations for various marks in the United States and other jurisdictions.
We have received U.S. trademark registrations for our corporate name and
logo, Coactinon(R) and Coviracil(R). We have received a Canadian trademark
registration for the mark Coviracil(R). We have also received registrations
in the European Union for the mark Coactinon(R) and our corporate logo. Our
pending application in the European Union for the mark Coviracil(TM) has been
opposed by Orsem, based on registrations for the mark Coversyl in various
countries, and Les Laboratories Serveir, based on a French registration for
the mark Coversyl. We do not believe that the marks Coviracil and Coversyl
are confusingly similar, but, in the event they are found to be confusingly
similar, we may need to adopt a different product name for emtricitabine in
the applicable jurisdictions. Several other companies use trade names that
are similar to our name for their businesses. If we are unable to obtain any
licenses that may be necessary for the use of our corporate name, we may be
required to change our name. Our management personnel were previously
employed by other pharmaceutical companies. The prior employers of these
individuals may allege violations of trade secrets and other similar claims
relating to their drug development activities for us.

THE COSTS AND TIME REQUIRED TO COMPLY WITH EXTENSIVE GOVERNMENT REGULATIONS
COULD PREVENT OR DELAY THE COMMERCIALIZATION OF OUR PRODUCTS.

In addition to preclinical testing, clinical trials and other approval
procedures for human pharmaceutical products, we are subject to numerous
domestic and international regulations covering the development of
pharmaceutical products. These regulations affect:

- manufacturing,

- safety,

- labeling,

- storage,

- record keeping,

- reporting, and

- marketing and promotion.

We must also comply with regulations governing non-clinical and
clinical laboratory practices, safe working conditions, and the use and
disposal of hazardous substances, including radioactive compounds and
infectious disease agents we use in connection with our development work. The
requirements vary widely from country to country and some requirements may
vary from state to state in the United States. We expect the process of
obtaining these approvals and complying with appropriate government
regulations to be time consuming and expensive. Even if our drug candidates
receive regulatory approval, we may still face difficulties in marketing and
manufacturing those drug candidates. Any approval may be contingent on
postmarketing studies or other conditions. The approval of any of our drug
candidates may limit the indicated uses of the drug candidate. A marketed
product, its manufacturer and the manufacturer's facilities are subject to
continual review and periodic inspections. The discovery of previously
unknown problems with a product, manufacturer or facility may result in
restrictions on the product or manufacturer, including withdrawal of the
product from the market. The failure to comply with applicable regulatory
requirements can, among other things, result in:

- fines,

- suspended regulatory approvals,

- refusal to approve pending applications,

- refusal to permit exports from the United States,

- product recalls,

- seizure of products,

- injunctions,

- operating restrictions, and

- criminal prosecutions.

In addition, adverse clinical results by others could negatively impact
the development and approval of our drug candidates. Some of our drug candidates
are intended for use as combination therapy with one or more other drugs, and
adverse safety, effectiveness or

regulatory developments in connection with the other drugs will also have an
adverse effect on our business.

INTENSE COMPETITION MAY RENDER OUR DRUG CANDIDATES NONCOMPETITIVE OR OBSOLETE.

We are engaged in segments of the drug industry that are highly
competitive and rapidly changing. Any of our current drug candidates that we
successfully develop will compete with numerous existing therapies. In addition,
many companies are pursuing novel drugs that target the same diseases we are
targeting. We believe that a significant number of drugs are currently under
development and will become available in the future for the treatment of HIV and
hepatitis B. We anticipate that we will face intense and increasing competition
as new products enter the market and advanced technologies become available. Our
competitors' products may be more effective, or more effectively marketed and
sold, than any of our products. Competitive products may render our products
obsolete or noncompetitive before we can recover the expenses of developing and
commercializing our drug candidates. Furthermore, the development of a cure or
new treatment methods for the diseases we are targeting could render our drug
candidates noncompetitive, obsolete or uneconomical. Many of our competitors:

- have significantly greater financial, technical and human resources
than we have and may be better equipped to develop, manufacture and
market products,

- have extensive experience in preclinical testing and clinical trials,
obtaining regulatory approvals and manufacturing and marketing
pharmaceutical products, and

- have products that have been approved or are in late stage development
and operate large, well-funded research and development programs.

Smaller companies may also prove to be significant competitors,
particularly through collaborative arrangements with large pharmaceutical and
biotechnology companies. Academic institutions, governmental agencies and other
public and private research organizations are also becoming increasingly aware
of the commercial value of their inventions and are more actively seeking to
commercialize the technology they have developed.

If we successfully develop and obtain approval for our drug candidates, we
will face competition based on many factors including:

- the safety and effectiveness of our products,

- the timing and scope of regulatory approvals,

- the availability of supply,

- marketing and sales capability,

- reimbursement coverage,

- price, and

- patent position.

Our competitors may develop or commercialize more effective or more
affordable products, or obtain more effective patent protection, than we do.
Accordingly, our competitors may commercialize products more rapidly or
effectively than we do, which could hurt our competitive position.

IF OUR LICENSORS TERMINATE THEIR AGREEMENTS WITH US, WE COULD LOSE OUR RIGHTS
TO OUR DRUG CANDIDATES.

We have licensed or obtained an option to license our drug candidates
under agreements with our licensors. These agreements permit our licensors to
terminate the agreements in circumstances such as our failure to achieve
development milestones or the occurrence of an uncured material breach by us.
The termination of any of these agreements would result in the loss of our
rights to a drug candidate. On the termination of most of our license
agreements, we are required to return the licensed technology to our
licensors. In addition, most of these agreements provide that we generally
must reimburse our licensors for the costs they incur in performing any
patent prosecution activities such as litigation, patent conflict, patent
opposition or other actions, for the technology licensed to us. We believe
that these costs as well as other costs under our license and option
agreements will be substantial and may increase significantly during the next
several years. Our inability or failure to pay any of these costs with
respect to any drug candidate could result in the termination of the license
or option agreement for the drug candidate.

IF WE ARE NOT ABLE TO SUCCESSFULLY MANUFACTURE OUR DRUG CANDIDATES, OUR
BUSINESS MAY NEVER ACHIEVE PROFITABILITY.

We do not have any internal manufacturing capacity and we rely on third
party manufacturers for the manufacture of all of our clinical trial
material. We plan to expand our existing relationships or to establish
relationships with additional third party manufacturers for products that we
develop. The terms of the Abbott Alliance provide that Abbott Laboratories
will manufacture all or a portion of our product requirements for those
products that are or become covered by the Abbott Alliance. We may be unable
to maintain our relationship with Abbott or to establish or maintain
relationships with other manufacturers on acceptable terms, and manufacturers
may be unable to manufacture products in commercial quantities on a cost
effective basis. Our dependence on third parties for the manufacture of our
products may adversely affect our profit margins and our ability to develop
and commercialize products on a timely and competitive basis. Further, third
party manufacturers may encounter manufacturing or quality control problems
in manufacturing our products and may be unable to maintain the necessary
governmental licenses and approvals to continue manufacturing our products.

BECAUSE WE DEPEND ON THIRD PARTIES, WE MAY BE UNABLE TO SUCCESSFULLY MARKET,
SELL OR DISTRIBUTE PRODUCTS WE DEVELOP.

In the United States, we currently intend to market the products
covered by the Abbott Alliance in collaboration with Abbott and to market
other products that we successfully develop, that do not become part of the
Abbott Alliance, through a direct sales force. Outside of the United States,
we expect Abbott to market products covered by the Abbott Alliance and, for
any other drug candidates that we successfully develop that do not become
part of the Abbott Alliance, we intend to market

and sell through arrangements or collaborations with third parties. In
addition, we expect Abbott to handle the distribution and sale of products
covered by the Abbott Alliance both inside and outside the United States.
With respect to the United States, our ability to market the products that we
successfully develop may be contingent on recruitment, training and
deployment of a sales and marketing force as well as the performance of
Abbott under the Abbott Alliance. We may be unable to establish marketing or
sales capabilities or to maintain arrangements or enter into new arrangements
with third parties to perform those activities on favorable terms. In
addition, third parties may have significant control or influence over
important aspects of the commercialization of our drug candidates, including
market identification, marketing methods, pricing, composition of sales force
and promotional activities. We may have limited control over the amount and
timing of resources that a third party devotes to our products. Our business
may never achieve profitability if we fail to establish or maintain a sales
force and marketing, sales and distribution capabilities.

BECAUSE WE DEPEND ON THIRD PARTIES FOR THE DISCOVERY AND DEVELOPMENT OF DRUG
CANDIDATES, WE MAY NOT SUCCESSFULLY ACQUIRE ADDITIONAL DRUG CANDIDATES OR
DEVELOP OUR CURRENT DRUG CANDIDATES.

We do not currently intend to engage in drug discovery. Our strategy for
obtaining additional drug candidates is to utilize the relationships of our
management team and scientific consultants to identify drug candidates for
in-licensing from companies, universities, research institutions and other
organizations. We may not succeed in acquiring additional drug candidates on
acceptable terms or at all.

Because we have engaged and intend to continue to engage third party
contract research organizations and other third parties to help us develop
our drug candidates, many important aspects of our drug development programs
have been and will continue to be outside of our direct control. In addition,
the contract research organizations may not perform all of their obligations
under arrangements with us. If the contract research organizations do not
perform clinical trials in a satisfactory manner or breach their obligations
to us, the development and commercialization of any drug candidate may be
delayed or precluded.

BECAUSE WE MAY NOT BE ABLE TO ATTRACT AND RETAIN KEY PERSONNEL AND ADVISORS,
WE MAY NOT SUCCESSFULLY DEVELOP OUR DRUG CANDIDATES OR ACHIEVE OUR OTHER
BUSINESS OBJECTIVES.

We are highly dependent on our senior management and scientific staff,
including Dr. David Barry, our Chairman and Chief Executive Officer. The loss
of the services of any member of our senior management or scientific staff
may significantly delay or prevent the achievement of product development and
other business objectives.

In order to pursue our drug development programs and marketing plans, we will
need to hire additional qualified scientific and management personnel.
Competition for qualified individuals is intense and we face competition from
numerous pharmaceutical and biotechnology companies, universities and other
research institutions. If we are not able to attract and retain these
individuals we may not be able to successfully commercialize our drug
candidates.

HEALTH CARE REFORM MEASURES AND THIRD PARTY REIMBURSEMENT PRACTICES ARE
UNCERTAIN AND MAY DELAY OR PREVENT THE COMMERCIALIZATION OF OUR DRUG
CANDIDATES.

The efforts of governments and third party payors to contain or reduce
the cost of health care will continue to affect the business and financial
condition of drug companies. A number of legislative and regulatory proposals
to change the health care system have been considered in recent years. In
addition, an increasing emphasis on managed care in the United States has and
will continue to increase pressure on drug pricing. We cannot predict whether
legislative or regulatory proposals will be adopted or what effect those
proposals or managed care efforts may have on our business. The announcement
and/or adoption of proposals could have an adverse effect on our ability to
earn profits and financial condition. Sales of prescription drugs depend
significantly on the availability of reimbursement to the consumer from third
party payors, such as government and private insurance plans. These third
party payors frequently require that drug companies give them predetermined
discounts from list prices, and they are increasingly challenging the prices
for medical products and services. Present combination treatment regimens for
the treatment of HIV are expensive and costs may increase as new combinations
are developed. These costs have resulted in limitations in the reimbursement
available from third party payors for the treatment of HIV infection, and we
expect these limitations will continue in the future. Third party payers may
not consider products we may bring to the market cost effective and may not
reimburse the consumer sufficiently to allow us to sell our products on a
profitable basis.

IF OUR PRODUCTS DO NOT ACHIEVE MARKET ACCEPTANCE, OUR BUSINESS MAY NEVER
ACHIEVE PROFITABILITY.

Our success will depend on the market acceptance of any products we
develop. The degree of market acceptance will depend on a number of factors,
including:

- the receipt and scope of regulatory approvals,

- the establishment and demonstration in the medical community of the
safety and effectiveness of our products and their potential
advantages over existing treatment methods, and

- reimbursement policies of government and third party payors.

Physicians, patients, payors or the medical community in general may not
accept or utilize any product that we may develop.

WE MAY NOT HAVE ADEQUATE INSURANCE PROTECTION AGAINST PRODUCT LIABILITY.

Our business exposes us to potential product liability risks that are
inherent in the testing of drug candidates and the manufacturing and marketing
of drug products and we may face product liability claims in the future. We
currently have only limited product liability insurance. We may be unable to
maintain our existing insurance and/or obtain additional insurance in the future
at a reasonable cost or in sufficient amounts to protect against potential
losses. A successful product liability claim or series of claims brought against
us could require us to pay substantial amounts that would decrease our
profitability, if any.

WE MAY INCUR SUBSTANTIAL COSTS RELATED TO OUR USE OF HAZARDOUS MATERIALS.

We use hazardous materials, chemicals, viruses and various radioactive
compounds in our drug development programs. Although we believe that our
handling and disposing of these materials comply with state and federal
regulations, the risk of accidental contamination or injury still exists. We
could be held liable for any damages or fines that result from any accidental
contamination or injury and the liability could exceed our resources.

OUR CONTROLLING STOCKHOLDERS MAY MAKE DECISIONS YOU DO NOT CONSIDER TO BE IN
YOUR BEST INTEREST.

As of May 31, 2001, our directors, executive officers and their
affiliates, excluding Abbott, owned approximately 15.6% of our outstanding
common stock and Abbott owned approximately 16.4% of our outstanding common
stock. Under the terms of the Abbott Alliance, Abbott has the right to
purchase additional shares of our common stock up to a maximum aggregate
percentage of 21% of our outstanding common stock and has rights to purchase
shares directly from us in order to maintain its existing level of ownership.
Abbott has the right to designate one person to serve as a member of our
Board of Directors. As a result, our controlling stockholders are able to
significantly influence all matters requiring stockholder approval, including
the election of directors and the approval of significant corporate
transactions. This concentration of ownership could also delay or prevent a
change in control of Triangle that may be favored by other stockholders.

THE MARKET PRICE OF OUR STOCK MAY FALL AS A RESULT OF MARKET VOLATILITY AND
FUTURE DEVELOPMENTS IN OUR INDUSTRY.

The market price of our common stock is likely to be volatile and could
fluctuate widely in response to many factors, including:

- announcements of the results of clinical trials by us or our
competitors,

- developments with respect to patents or proprietary rights,

- announcements of technological innovations by us or our competitors,

- announcements of new products or new contracts by us or our
competitors,

- actual or anticipated variations in our operating results due to the
level of development expenses and other factors,

- changes in financial estimates by securities analysts and whether our
earnings meet or exceed analysts' estimates,

- conditions and trends in the pharmaceutical and other industries,

- new accounting standards,

- general economic, political and market conditions and other factors,
and

- the occurrence of any of the risks described in these "Risk Factors."

In the past, following periods of volatility in the market price of the
securities of companies in our industry, securities class action law suits
have often been brought against those companies. If we face litigation in the
future, it would result in substantial costs and a diversion of management
attention and resources, which would negatively impact our business.

APPROXIMATELY 27,700,000 SHARES OF OUR COMMON STOCK MAY BE SOLD WITHOUT
RESTRICTION AND APPROXIMATELY 10,850,000 SHARES ARE REGISTERED FOR SALE.
SALES OF A LARGE NUMBER OF OUR SHARES MAY CAUSE OUR STOCK PRICE TO FALL EVEN
IF OUR BUSINESS IS DOING WELL.

If our stockholders sell a substantial number of shares of our common
stock in the public market, the market price of our common stock could
decline. As of May 31, 2001, there were 48,363,918 shares of common stock
outstanding, of which approximately 27,700,000 were immediately eligible for
resale in the public market without restriction. Holders of approximately
14,100,000 shares, including the shares offered by this prospectus, have
rights to cause us to register their shares for sale to the public. We have
filed registration statements to register the sale of approximately
10,850,000 of these shares, including the shares offered by this prospectus.
In addition, Abbott will have the right on or after June 30, 2002 to cause us
to register for resale in the public market the 6,571,428 shares of common
stock purchased at the closing of the Abbott Alliance.

Declines in our stock price might harm our ability to issue equity or
secure other types of financing arrangements. The price at which we issue
shares is generally based on the market price of our common stock and a
decline in our stock price would result in our needing to issue a greater
number of shares to raise a given amount of funds or acquire a given amount
of goods or services. For this reason, a decline in our stock price might
also result in increased ownership dilution to our stockholders. A low stock
price might impair our ability to raise capital under our Facility because
Ramius Securities is not obligated to sell our common stock under the
Facility on a given day if our average stock price during that day is less
than $4.00 per share or less than any higher floor price specified by us.

The perceived risk associated with the possible sale of a large number
of shares under the Facility could cause some of our stockholders to sell
their stock, causing the price of our stock to decline. In addition, actual
or anticipated downward pressure on our stock price could cause some
institutions or individuals to engage in short sales of our common stock,
which may itself cause the price of our stock to decline.

ANTITAKEOVER PROVISIONS IN OUR CHARTER DOCUMENTS AND DELAWARE LAW COULD DELAY,
DEFER OR PREVENT A TENDER OFFER OR TAKEOVER ATTEMPT THAT YOU CONSIDER TO BE IN
YOUR BEST INTEREST.

We have adopted a number of provisions that could have antitakeover
effects. We have adopted a preferred stock purchase rights plan, commonly
referred to as a "poison pill." The rights plan is intended to deter an
attempt to acquire Triangle in a manner or on terms not approved by the Board
of Directors. The rights plan will not prevent an acquisition of Triangle
which is approved by the Board of Directors. Our charter authorizes the Board
of Directors to determine the terms of any shares of undesignated preferred
stock and issue them without stockholder approval. The issuance of preferred
stock may make it more difficult for a third party to acquire, or may
discourage a third party from acquiring, voting control of Triangle. Our
bylaws divide the Board of Directors into three classes of directors with
each class serving a three year term. These and other provisions of our
charter and our bylaws, as well as provisions of Delaware law, could delay or
impede the removal of incumbent directors and could make more difficult a
merger, tender offer or proxy contest involving Triangle, even if the events
could be beneficial to our stockholders. These provisions could also limit
the price that investors might be willing to pay for our common stock.

III. FORWARD-LOOKING STATEMENTS

This prospectus contains "forward-looking statements" within the
meaning of the Private Securities Litigation Reform Act of 1995. All
statements, other than statements of historical facts, included in, or
incorporated by reference into this prospectus, are forward-looking
statements. In addition, when we use the words "anticipate", "estimate",
"project", and similar expressions in this document, we are identifying
forward-looking statements. These forward-looking statements are subject to
various risks and uncertainties and are based on our assumptions. Should one
or more of these risks or uncertainties materialize, or should our underlying
assumptions prove incorrect, actual results may vary materially from those

we anticipate, estimate or project. We cannot assure you that our
expectations will prove to have been correct. We have outlined risks we can
identify under "Risk Factors," which may cause our or our industry's actual
results, levels of activity, performance or achievements to be materially
different from future results, levels of activity, performance or
achievements expressed or implied by these forward-looking statements.

Although we believe that the expectations reflected in the forward-looking
statements are reasonable, we cannot guarantee future results, levels of
activity, performance or achievements. Moreover, neither we nor any other person
assumes responsibility for the accuracy and completeness of these statements. We
are under no duty to update any of the forward-looking statements after the date
of this prospectus or to conform these statements to actual results unless
required by law.

IV. USE OF PROCEEDS

We will not receive any of the proceeds from the sale of the shares by the
selling stockholders.

V. SELLING STOCKHOLDERS

We are registering all 2,000,000 shares of common stock covered by this
prospectus on behalf of the selling stockholders named in the table below. We
issued all of the shares to the selling stockholders on May 18, 2001 on the
conversion of all outstanding Series B preferred stock. We issued the Series B
preferred stock to the selling stockholders in a private placement completed on
March 9, 2001. We have registered the shares of common stock to permit the
selling stockholders and their pledgees, donees, transferees or other
successors-in-interest that receive their shares from a selling stockholder as a
gift, partnership distribution or other non-sale related transfer after the date
of this prospectus to resell the shares when they deem appropriate.

We have agreed to file any amendments and supplements to the registration
statement that are necessary to keep the registration statement effective until
the earlier of the date on which all of the shares are sold or two years from
the effective date of the registration statement.

The following table contains:

- the name of each of the selling stockholders,

- the number of shares owned by each of the selling stockholders as of
June 30, 2001,

- the number of shares that may be offered under this prospectus, and

- the number of shares of our common stock owned by each of the selling
stockholders after this offering is completed.

Except as described in the table below, none of the selling
stockholders has had a material relationship with us within the past three years
other than as a result of the ownership of the shares or other securities of
Triangle. The number of shares in the column "Number of Shares Being Offered"
represent all of the shares that each selling stockholder may offer under this
prospectus. We do not know how long the selling stockholders will hold the
shares before selling them or if they will sell them and we currently have no
agreements, arrangements or understandings with any of the selling stockholders
regarding the sale of any of the shares.

This registration statement will also cover any additional shares of
common stock which are issued to the selling stockholders as a result of any
stock dividend, stock split, recapitalization or other similar transaction which
results in an increase in the number of Triangle's outstanding shares of common
stock.

Except as indicated in the table below, each person has sole investment
and voting power with respect to the shares listed in the table. For purposes
of this table, a person or group of persons is deemed to have "beneficial
ownership" of any shares which the person has the right to acquire within 60
days. Percentage ownership is based on 48,363,918 shares of common stock of
Triangle outstanding on June 30, 2001. For purposes of computing the
percentage of outstanding shares held by each person named below, any
security which a person has the right to acquire within 60 days is deemed to
be outstanding for the purpose of computing the percentage ownership for that
person, but is not deemed to be outstanding for the purpose of computing the
percentage ownership for other persons.

SHARES SHARES
BENEFICIALLY OWNED BENEFICIALLY OWNED
PRIOR TO OFFERING NUMBER OF AFTER OFFERING (1)
------------------ SHARES BEING -------------------
NAME OF SELLING STOCKHOLDER NUMBER PERCENT OFFERED NUMBER PERCENT
--------------------------------- ------ ------- ----------- ------ -------

Alta BioPharma Partners, L.P. 1,045,920 2.2% 424,330 621,590 1.3%

Forward Ventures IV, L.P. (2) 1,229,130 2.5 1,229,130 0 *

Forward Ventures IV B, L.P. (2) 104,200 * 104,200 0 *
Triangle Pharmaceuticals Chase
Partners (Alta Bio), LLC 597,330 1.2 242,340 354,990 *
--------- --- --------- -------
TOTAL 2,976,580 2,000,000 976,580
--------- --------- -------
--------- --------- -------

-----------------------------------
* Represents beneficial ownership of less than one percent.

(1)Assumes the sale of all shares offered by this prospectus and no
other purchases or sales of Triangle's common stock.

(2)The general partner of each of Forward Ventures IV, L.P. and Forward
Ventures IV B, L.P. is Forward IV Associates, LLC. The Managing Member of
Forward IV Associates, LLC, Standish Fleming, is a member of the Board of
Directors of Triangle.

VI. PLAN OF DISTRIBUTION

The selling stockholders or donees or pledgees of any selling
stockholders may effect the sale or distribution of the shares directly to
purchasers as principals or through one or more underwriters, brokers,
dealers or agents from time to time in one or more transactions, which may
involve crosses or block transactions, or

(i) on any exchange or in the over-the-counter market,

(ii) in transactions otherwise than in the over-the counter
market,

(iii) through the writing of put or call options, whether
the options are listed on an options exchange or
otherwise,

(iv) through the distribution of the shares by any selling
stockholder to its partners, members or shareholders, or

(v) through a combination of any of the above.

Any of these transactions may be effected at market prices, at prices
related to market prices, at prices determined at the time of sale or at
negotiated or fixed prices, in each case as determined by the selling
stockholder or by agreement between the selling stockholder and underwriters,
brokers, dealers, agents or purchasers. If the selling stockholders effect
transactions by selling shares to or through underwriters, brokers, dealers
or agents, the underwriters, brokers, dealers or agents may receive
compensation in the form of discounts, concessions or commissions from the
selling stockholders or commissions from purchasers of shares for whom they
may act as agent, which discounts, concessions or commissions as to
particular underwriters, brokers, dealers or agents may be in excess of those
customary in the types of transactions involved. Brokers, dealers or agents
and any other participating brokers, dealers or the selling stockholders may
be deemed to be "underwriters" within the meaning of Section 2(11) of the
Securities Act, in connection with sales of the shares. Accordingly, any
commission, discount or concession received by them and any profit on the
resale of the shares purchased by them may be deemed to be underwriting
discounts or commissions under the Securities Act. Because selling
stockholders may be deemed to be "underwriters" within the meaning of Section
2(11) of the Securities Act, the selling stockholders will be subject to the
prospectus delivery requirements of the Securities Act.

The selling stockholders may enter into hedging transactions with
broker-dealers or other financial institutions. In connection with hedging
transactions, broker-dealers or other financial institutions may engage in
short sales of Triangle's common stock in the course of hedging the positions
they assume with selling stockholders. The selling stockholders may also
enter into options or other transactions with broker-dealers or other
financial institutions which require the delivery to the broker-dealer or
other financial institution of shares offered under this prospectus. The
broker-dealer or other financial institution may then resell those shares
pursuant to this prospectus, as supplemented or amended to reflect the
transaction.

Under the securities laws of some states, the shares may be sold in those
states only through registered or licensed brokers or dealers. In addition, in
some states the shares may not be sold unless the shares have been registered or
qualified for sale in the state or an exemption from registration or
qualification is available and is complied with.

Selling stockholders may also resell all or a portion of the shares in
open market transactions in reliance on Rule 144 under the Securities
Act, rather than under this prospectus, provided they meet the criteria and
conform to the requirements of Rule 144.

Under applicable rules and regulations under the Securities Exchange
Act of 1934, as amended, any person engaged in the distribution of the shares
may not simultaneously engage in market making activities with respect to our
common stock for a period of two business days prior to the commencement of
the distribution. In addition,

each selling stockholder will be subject to applicable provisions of the
Exchange Act and the associated rules and regulations under the Exchange Act,
including Regulation M, which provisions may limit the timing of purchases
and sales of shares of our common stock by the selling stockholders. We will
make copies of this prospectus available to the selling stockholders and have
informed them of the need to deliver copies of this prospectus to purchasers
at or prior to the time of any sale of the shares.

We will pay all of the expenses incident to the registration, offering
and sale of the shares to the public under this prospectus other than
commissions, fees and discounts of underwriters, brokers, dealers and agents.
We have agreed to indemnify the selling stockholders against a number of
liabilities, including liabilities under the Securities Act. We will not
receive any of the proceeds from the sale of any of the shares by the selling
stockholders.

We have agreed to keep the Registration Statement of which this
prospectus constitutes a part effective until the earlier of the date on
which all of the shares are sold or two years from the effective date of the
Registration Statement.

VII. LEGAL MATTERS

For purposes of this offering, Brobeck, Phleger & Harrison LLP, New York,
New York, is giving its opinion as to the validity of the shares.

VIII. EXPERTS

The financial statements incorporated in this prospectus by reference to
the Annual Report on Form 10-K of Triangle for the year ended December 31, 2000,
have been incorporated in reliance on the report of PricewaterhouseCoopers LLP,
independent accountants, given on the authority of that firm as experts in
auditing and accounting.

IX. WHERE YOU CAN FIND MORE INFORMATION

We file reports, proxy statements and other information with the SEC.
You may read and copy any document we file at the SEC's public reference
rooms in Washington, D.C., New York, New York and Chicago, Illinois. Please
call the SEC at 1-800-SEC-0330 for further information on the public
reference rooms. Our SEC filings are also available to the public on the
SEC's website at http://www.sec.gov.

X. INFORMATION INCORPORATED BY REFERENCE

The SEC allows us to "incorporate by reference" the information we file
with them, which means that we can disclose important information to you by
referring you to those documents. The information incorporated by reference is
considered part of this prospectus. We incorporate by reference the documents
listed below and any future filings we make with the SEC under Section 13(a),
13(c), 14, or 15(d) of the Securities Exchange Act of 1934 until this offering
is complete.

1. Our Quarterly Report on Form 10-Q for the quarterly period ended
March 31, 2001 filed on May 10, 2001;

2. Our Annual Report on Form 10-K for the fiscal year ended December 31,
2000 filed on February 26, 2001, including information in our
Definitive Proxy Statement in connection with our 2001 Annual Meeting
of Stockholders; and

3. The description of our common stock contained in our Registration
Statements on Form 8-A filed October 18, 1996, February 10, 1999, and
June 18, 1999.

The reports and other documents that we file after the date of this
prospectus will update and supersede the information in this prospectus.

We will provide a copy of these filings, at no cost, if you so request by
writing or telephoning us at:

Triangle Pharmaceuticals, Inc.
4611 University Drive
P.O. Box 50530
Durham, North Carolina, 27717
(919) 493-5980
Attn: General Counsel

WE HAVE NOT AUTHORIZED ANY PERSON TO MAKE A STATEMENT THAT DIFFERS FROM WHAT IS
IN THIS PROSPECTUS. IF ANY PERSON DOES MAKE A STATEMENT THAT DIFFERS FROM WHAT
IS IN THIS PROSPECTUS, YOU SHOULD NOT RELY ON IT. THIS PROSPECTUS IS NOT AN
OFFER TO SELL, NOR IS IT AN OFFER TO BUY, THESE SECURITIES IN ANY STATE IN WHICH
THE OFFER OR SALE IS NOT PERMITTED. THE INFORMATION IN THIS PROSPECTUS IS
COMPLETE AND ACCURATE AS OF ITS DATE, BUT THE INFORMATION MAY CHANGE AFTER THAT
DATE.

2,000,000 Shares

TRIANGLE
PHARMACEUTICALS, INC.

COMMON STOCK

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PROSPECTUS
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JULY 11, 2001