PTC Therapeutics Provides Corporate Update and Reports Third Quarter Financial Results - Third quarter 2023 total revenues of $197 million and remain on target for 2023 revenue guidance - - PTC strengthened its financial

PTC Therapeutics Provides Corporate Update and

Reports Third Quarter Financial Results

- Third quarter 2023 total revenues of $197 million and remain on target for 2023 revenue guidance -

- PTC strengthened its financial position following recent restructuring initiatives and Royalty Pharma transaction -

- PTC provides regulatory updates for pipeline programs -

SOUTH PLAINFIELD, N.J., October 26, 2023 - PTC Therapeutics, Inc., (NASDAQ: PTCT) today announced a corporate update and financial results for the third quarter ending September 30, 2023.

"I am very proud of the progress all of our teams made this quarter," said Matthew Klein, M.D., Chief Executive Officer, PTC Therapeutics, Inc. "The recent Royalty Pharma transaction and restructuring initiatives that we implemented have put the company on a strong financial footing. We believe we are well positioned to deliver on our most promising opportunities for growth, including the potential sepiapterin revenue opportunity of more than $1 billion and the PTC518 HD program."

Key Corporate Updates:

oTranslarna (ataluren) quarterly net product revenue was $69 million, with new patients in existing geographies and continued geographic expansion.

oEmflaza (deflazacort) quarterly net product revenue was $67 million, with new patient starts and high compliance.

Key Clinical and Regulatory Updates:

Third Quarter 2023 Financial Highlights:

PTC Updates Full Year 2023 Financial Guidance as Follows:

Non-GAAP Financial Measures:

In this press release, the financial results of PTC are provided in accordance with GAAP and using certain non-GAAP financial measures. In particular, the non-GAAP R&D and SG&A expense financial measures exclude non-cash, stock-based compensation expense. These non-GAAP financial measures are provided as a complement to financial measures reported in GAAP because management uses these non-GAAP financial measures when assessing and identifying operational trends. In management's opinion, these non-GAAP financial measures are useful to investors and other users of PTC's financial statements by providing greater transparency into the historical and projected operating performance of PTC and the company's future outlook. Non-GAAP financial measures are not an alternative for financial measures prepared in accordance with GAAP. Quantitative reconciliations of the non-GAAP financial measures to their respective closest equivalent GAAP financial measures are included in the table below.

PTC Therapeutics, Inc.

Consolidated Statements of Operations

(In thousands, except share and per share data)

PTC Therapeutics, Inc.

Summary Consolidated Balance Sheets

(in thousands, except share data)

PTC Therapeutics, Inc.

Reconciliation of GAAP to Non-GAAP Projected Full Year 2023 R&D and SG&A Expense

BLA: Biologics License Application

CHF: Confoederatio Helvetica Francs (Swiss francs)

CHMP: Committee for Medicinal Products for Human Use

DMD: Duchenne Muscular Dystrophy

EMA: European Medicines Agency

FA: Friedreich Ataxia

FDA: U.S. Food and Drug Administration

GAAP: Generally Accepted Accounting Principles

HD: Huntington's Disease

NDA: New Drug Application

PKU: Phenylketonuria

R&D: Research and Development

SG&A: Selling, General and Administrative

SMA: Spinal Muscular Atrophy

STRIDE: Strategic Targeting of Registries and International Database of Excellence

Today's Conference Call and Webcast Reminder:

To access the call by phone, please click here to register and you will be provided with dial-in details. To avoid delays, we recommend participants dial in to the conference call 15 minutes prior to the start of the call. The webcast conference call can be accessed on the Investor section of the PTC website at https://ir.ptcbio.com/events-presentations. A replay of the call will be available approximately two hours after completion of the call and will be archived on the company's website for 30 days following the call.

About PTC Therapeutics, Inc.

For More Information:

Forward-Looking Statements:

This press release contains forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. All statements contained in this release, other than statements of historic fact, are forward-looking statements, including the information provided under the heading "PTC Updates Full Year 2023 Revenue Guidance as Follows", including with respect to (i) 2023 total revenue guidance, (ii) 2023 net product revenue guidance for the DMD franchise, (iii) 2023 GAAP and non-GAAP R&D and SG&A expense guidance and (iv) 2023 acquisition related one-time expense guidance, and statements regarding: the future expectations, plans and prospects for PTC, including with respect to the expected timing of clinical trials and studies, availability of data, regulatory submissions and responses, commercialization and other matters with respect to its products and product candidates; PTC's strategy, future operations, future financial position, future revenues, projected costs; the extent, timing and financial aspects of our strategic pipeline prioritization and reductions in workforce; and the objectives of management. Other forward-looking statements may be identified by the words, "guidance", "plan," "anticipate," "believe," "estimate," "expect," "intend," "may," "target," "potential," "will," "would," "could," "should," "continue," and similar expressions.

PTC's actual results, performance or achievements could differ materially from those expressed or implied by forward-looking statements it makes as a result of a variety of risks and uncertainties, including those related to: the outcome of pricing, coverage and reimbursement negotiations with third party payors

for PTC's products or product candidates that PTC commercializes or may commercialize in the future; PTC's ability to maintain its marketing authorization of Translarna for the treatment of nmDMD in Brazil, Russia, the European Economic Area (EEA) and other regions, including whether the European Medicines Agency (EMA) determines in the re-examination process of the Committee for Medicinal Products for Human Use's negative opinion that the benefit-risk balance of Translarna authorization supports renewal of such authorization; PTC's ability to complete Study 041, which is a specific obligation to continued marketing authorization in the EEA; PTC's ability to utilize results from Study 041, a randomized, 18-month, placebo-controlled clinical trial of Translarna for the treatment of nmDMD followed by an 18-month open-label extension, to support a renewal of the conditional marketing authorization for Translarna for the treatment of nmDMD in the EEA and to support a marketing approval for Translarna for the treatment of nmDMD in the United States; whether investigators agree with PTC's interpretation of the results of clinical trials and the totality of clinical data from our trials in Translarna; expectations with respect to Upstaza, including any regulatory submissions and potential approvals, commercialization, manufacturing capabilities, the potential achievement of development, regulatory and sales milestones and contingent payments that PTC may be obligated to make; expectations with respect to the commercialization of Evrysdi under our SMA collaboration; expectations with respect to the commercialization of Tegsedi and Waylivra; the timing of and actual expenses incurred in connection with the discontinuation of PTC's preclinical and early research programs in gene therapy and reductions in workforce, which may be in different periods and may be materially higher than estimated; the savings that may result from the discontinuation of PTC's strategic pipeline prioritization and reductions in workforce, which may be materially less than expected; significant business effects, including the effects of industry, market, economic, political or regulatory conditions; changes in tax and other laws, regulations, rates and policies; the eligible patient base and commercial potential of PTC's products and product candidates; PTC's scientific approach and general development progress; the potential financial impact and benefits of PTC's leased biologics manufacturing facility; PTC's ability to satisfy its obligations under the terms of its lease agreements, including for its leased biologics manufacturing facility; the sufficiency of PTC's cash resources and its ability to obtain adequate financing in the future for its foreseeable and unforeseeable operating expenses and capital expenditures; and the factors discussed in the "Risk Factors" section of PTC's most recent Quarterly Report on Form 10-Q and Annual Report on Form 10-K, as well as any updates to these risk factors filed from time to time in PTC's other filings with the SEC. You are urged to carefully consider all such factors.

As with any pharmaceutical under development, there are significant risks in the development, regulatory approval and commercialization of new products. There are no guarantees that any product will receive or maintain regulatory approval in any territory, or prove to be commercially successful, including Translarna, Emflaza, Upstaza, Evrysdi, Tegsedi or Waylivra.

The forward-looking statements contained herein represent PTC's views only as of the date of this press release and PTC does not undertake or plan to update or revise any such forward-looking statements to reflect actual results or changes in plans, prospects, assumptions, estimates or projections, or other circumstances occurring after the date of this press release except as required by law.