For Immediate Release

PTC THERAPEUTICS RAISES ADDITIONAL $40 MILLION TO ADVANCE ITS INTERNAL RNA-BASED DRUG DISCOVERY PROGRAMS

September 19, 2001

SOUTH PLAINFIELD, N.J., -- PTC Therapeutics Inc. (PTC), a privately held biopharmaceutical company, announced today it has received $40 million to advance drug discovery efforts based on its proprietary integrated ribonucleic acid (RNA) biology and chemistry programs. CSFB Private Equity, Vulcan Ventures, and Bay City Capital led this round of financing. Other investors in this round include CDIB Biotech, Inc., China Development Industrial Bank, Delphi Ventures, HealthCap, The Manufacturers Life Insurance Company (U.S.A.), NMT New Medical Technologies, Novo A/S, and Pictet Global Sector Fund - Biotech. PTC's shareholders also include Tularik Inc., Three Crowns Capital, and the University of Medicine and Dentistry of New Jersey (UMDNJ).

"We believe PTC Therapeutics is well positioned to become the biotechnology leader in this emerging field of small molecules that interact with RNA,'' said Andrew Schwab, Principal, Bay City Capital, commenting on this latest financing round. ``While RNA has been an interesting target for many years, PTC has assembled the people and tools to make a significant effort towards developing a broad range of novel products in this field."

"This additional funding will support and accelerate our drug discovery projects, particularly in the areas of infectious diseases and oncology where new therapeutic options are urgently needed,'' said Stuart Peltz, Ph.D., President and CEO of PTC Therapeutics. ``Since our last financing round we have put in place a scientific team of the highest caliber that includes several recognized leaders in the fields of RNA biology and chemistry. We look forward to continued expansion and rapid execution of our business goals and appreciate the continuing support of our previous investors while welcoming our new investors."

PTC completed its first large round of financing in September 2000, raising $15 million, which enabled the Company to build a 30,000 sq. ft. site and to recruit an initial team of fifty experienced scientists and managers. The current financing round will allow PTC to advance the next phase by increasing the staffing and resources applied to its drug discovery programs. Capital raised in this round brings PTC's total funding to date to over $56 million.

Upon closing of this financing round, PTC appointed to the Board of Directors Mr. Andrew Schwab, Principal, Bay City Capital and Mr. Soren Carlsen, Chief Science Officer for Novo A/S. Continuing members of PTC's Board of Directors are Ms. Ruth Kunath of Vulcan Ventures, Inc.; Mr. Michael Schmertzler, of an investment advisor to Credit Suisse First Boston Equity Partners, L.P.; Mr. Peter Svennilson of Three Crowns Capital; Dr. Marc Ostro, formerly Senior Managing Director of KPMG and a founder of The Liposome Company; Dr. Harvey J. Berger, Chairman and Chief Executive Officer of ARIAD Pharmaceuticals, Inc.; and, Dr. Bill Stephenson, Vice President of Research, University of Medicine and Dentistry of New Jersey.

PTC Therapeutics, Inc. applies its integrated RNA biology and chemistry proprietary drug-discovery platforms to identify small molecule drugs. PTC's technologies allow drug discovery programs to progress rapidly from gene sequencing to lead compounds by identifying small molecules that selectively bind to either RNA targets or proteins that interact with RNA. PTC's technology provides a general approach for all genetic-based diseases and the Company currently has drug discovery programs in oncology, infectious diseases, inflammation, and genetic disorders.

About the Investors:

Bay City Capital

Bay City Capital is a San Francisco-based private merchant bank that focuses exclusively on the life sciences industry, including the pharmaceutical, biomedical, life sciences information technology, and nutrition and agribusiness sectors. BCC provides investment capital and strategic and transaction advisory services to publicly traded and privately held companies. Since inception in 1997, the firm has committed over $450 million across four investment funds, BCC Funds I, II, and III and the North American Nutrition and Agribusiness Fund, with plans to expand its funds continuously over time. More information about Bay City Capital can be found at www.baycitycapital.com.

CDIB Biotech, Inc.

CDIB Biotech, Inc. is a Chicago based private company, which is wholly owned by the China Development Industrial Bank in Taiwan. CDIB Biotech provides venture capital and expertise to early-late development stage companies focused on life sciences. Since the inception of it's US biotech fund, in early 2001, CDIB Biotech has rapidly expanded a portfolio of venture capital investments. More information about CDIB Biotech can be found at <http://www.cdibbiotech.com>.

China Development Industrial Bank Inc. (CDIB) CDIB is the largest and most prestigious investment bank in Taiwan. With total assets of $5.4B, and net income of $418M in 2000, CDIB actively provides venture capital and local strengths for all stages high-tech companies around the world. Currently, CDIB has invested in 63 biotech companies, a total amount of $150M. More information about CDIB can be found at <http://www.cdibank.com>.

CSFB Private Equity

CSFB Private Equity, the global private equity arm of Credit Suisse First Boston, is one of the largest managers of alternative assets in the world, with over $25 billion in funds under management. CSFB Private Equity is comprised of investment funds that focus on domestic and international leveraged buyouts and other private equity investments, including mezzanine, real estate, venture capital and investments in other funds. CSFB Private Equity includes the family of DLJ Merchant Banking funds and the Sprout funds. CSFB Private Equity maintains offices in New York, London, Buenos Aires, Chicago, Hong Kong, Los Angeles, Menlo Park, San Francisco, Sao Paulo and Tokyo.

Delphi Ventures

Delphi Ventures is a private venture capital firm providing equity financing and supportive business expertise to young biomedical and healthcare companies. Our goal is to contribute added value to the companies we fund by serving as active investors. Since our formation in 1988 Delphi has invested in over 100 companies encompassing every segment of the biomedical field including: Biopharmaceuticals/Drug Discovery Tool, Medical Devices and Diagnostics and Healthcare Services.

HealthCap

HealthCap is a family of venture capital funds managed by the Odlander Fredrikson Group. With a committed capital of approximately $300 million, HealthCap is the largest specialized provider of venture capital within life sciences in the Nordic countries and one of the largest independent actors in the sector in Europe. HealthCap invests in early stage opportunities as well as more mature companies on a global basis. More information about HealthCap can be found at http://www.healthcap.se.

The Manufacturers Life Insurance Company (U.S.A.), on behalf of MCC Life Sciences Opportunity Fund, LLC.

MCC Life Sciences Opportunity Fund, LLC is a venture capital fund with an investment objective of achieving long-term growth of capital by investing primarily in early-stage companies that expect to commercialize innovativelife sciences technology.

NMT New Medical Technologies

NMT New Medical Technologies is the first healthcare venture capital company in Switzerland, specializing in start-up companies and other selected investments. Its main objective is to start and build up globally competitive companies in the Alpine Rim. NMT seeks investment opportunities in breakthrough biopharmaceutical and medical technologies from universities and other private entities, as well as spin-offs from large corporations. NMT also makes carefully timed, value-driven investments in existing, late-stage private and promising small public companies on a worldwide basis, especially in the USA. Since the capital increase of November 2000, NMT operates with a committed capital of CHF 296 million. More information about NMT can be found at http://www.nmt.ch.

Novo A/S

Novo A/S is a private company, wholly owned by the Novo Nordisk Foundation. Novo A/S provides venture capital and expertise for development stage companies with a pioneering concept within life-sciences. Novo A/S has a rapidly expanding portfolio of venture capital investments. Furthermore, Novo A/S holds significant share holdings in Novo Nordisk A/S and Novozymes A/S. More information about Novo A/S can be found at http://www.novo.dk.

Vulcan Ventures

Vulcan Ventures of Seattle was founded by Paul G. Allen in 1986 to research and implement his investments. Through Vulcan Ventures, Allen invests in a suite of companies that offer products, services or technologies that fit his Wired World strategy and can contribute to or benefit from the technology and strategy of other companies within the group's extensive investment portfolio.

Pictet Global Sector Fund - Biotech

Pictet Global Sector Fund - Biotech is a Luxembourg investment fund with UCITS status investing in transferable securities of the biopharmaceutical sector. Created in March 1995, the fund has assets of USD1.325bn (as of September 10) and is presently registered in the main European continental countries for public distribution.

Three Crowns Capital Ltd.

Three Crowns Capital (TCC), fully owned by Peter Svennilson, is a Bermuda based company that focuses exclusively on helping start and develop biotech companies. TCC has assisted numerous companies including: Tularik, Rosetta, Sunesis, Somalogic, Chemocentryx and PTC. Since end of 1996 TCC has assisted these companies in raising approx $450 million in private equity.

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