HOOKIPA Reports Fourth Quarter and Full Year 2022 Financial Results and Provides 2023 Outlook Data from Phase 2 study of HB-200 in combination with pembrolizumab in head and neck cancers expected in 2Q 2023 Phase 1 HB-30

HOOKIPA Reports Fourth Quarter and Full Year 2022 Financial Results

and Provides 2023 Outlook

NEW YORK and VIENNA, March 15, 2023 - HOOKIPA Pharma Inc. (NASDAQ: HOOK, HOOKIPA'), a company developing a new class of immunotherapeutics based on its proprietary arenavirus platform, today reported financial results and provided a corporate update for the fourth quarter and full year 2022, as well as the outlook for 2023.

"We made substantial progress in 2022 as we work to develop our novel arenaviral immunotherapies against a variety of cancers and infectious diseases. Our lead candidate, HB-200, advanced to Phase 2 in combination with pembrolizumab for head and neck cancers; our HB-300 program in prostate cancer advanced toward the clinic with IND acceptance; and we added a strategic collaboration with Roche to develop our HB-700 program for KRAS-mutated cancers," said Joern Aldag, Chief Executive Officer at HOOKIPA. "We have started the year strongly with our HB-300 program now open for enrollment, and our HB-700 program achieving a key milestone as we move toward the clinic. We remain focused on driving our rich pipeline forward and generating clinical data that expands the evidence of our arenaviral platform technology to help address unmet needs in cancer."

With a focus on its oncology portfolio, HOOKIPA advanced programs in each of the three pillars of its oncology strategy: targeting oncoviral antigens (HB-200); targeting self-antigens (HB-300); and targeting shared neoantigens (HB-700).

Infectious Disease Portfolio

Fourth Quarter and Full Year 2022 Financial Results

Cash Position: HOOKIPA's cash, cash equivalents and restricted cash as of December 31, 2022 was $113.4 million compared to $66.9 million as of December 31, 2021. The increase was primarily attributable to funds resulting from the amended and restated Gilead collaboration agreement, the strategic collaboration and licensing agreement with Roche and the follow-on financing in March 2022, partly offset by cash used in operating activities.

HOOKIPA's cash position as of December 31, 2022 does not include a $5 million milestone payment that the Company received under the amended and restated Gilead collaboration agreement and a $10 million milestone payment that HOOKIPA received under the strategic collaboration and licensing agreement with Roche.

HOOKIPA does not hold cash deposits or securities at Silicon Valley Bank.

Revenue: Revenue was $7.8 million for the three months ended December 31, 2022, and $14.2 million for the year ended December 31, 2022 compared to $3.9 million for the three months ended December 31, 2021 and $18.4 million for the year ended December 31, 2021. The decrease in the full year revenues was primarily due to lower cost reimbursements received under the collaboration agreement with Gilead. This decrease was partially offset by the recognition of a milestone payment for supporting Gilead to progress with a Phase 1 clinical trial for the HBV program. A substantial part of the $4.0 million milestone payment and the $15.0 million initiation fee that were received for the HIV program under the restated Gilead collaboration agreement in the three months ended March 31, 2022, and the main part of the $25.0 million upfront payment that was received under the strategic collaboration and licensing agreement with Roche in the three months ended December 31, 2022, remained recorded as deferred revenue to be recognized in future accounting periods.

Research and Development Expenses: HOOKIPA's research and development expenses were $17.6 million for the three months ended December 31, 2022, and $68.6 million for the year ended December 31, 2022 compared to $22.4 million for the three months ended December 31, 2021, and $82.9 million for the year ended December 31, 2021. The primary drivers of the decrease in research and development expenses by $14.3 million compared to the year ended December 31, 2021 were lower manufacturing expenses for our HB-200, HB-300 and Gilead partnered programs and lower clinical study expenses due to the completion of patient enrollment of the Phase 2 trial for our HB-101 program, a decrease in personnel related expenses including stock based compensation, and a decrease in laboratory consumables, partially offset by an increase in professional and consulting fees and an increase in training and recruitment expenses.

General and Administrative Expenses: General and administrative expenses amounted to $3.8 million for the three months ended December 31, 2022 and $18.8 million for the year ended December 31, 2022 compared to $3.5 million for the three months ended December 31, 2021, and $17.3 million for the year ended December 31, 2021. The increase was primarily due to an increase in professional and consulting fees and an increase in training and recruitment expenses, partially offset by a decrease in personnel-related expenses and a decrease in other expenses.

Net Loss: HOOKIPA's net loss was $12.3 million for the three months ended December 31, 2022 and $64.9 million for the year ended December 31, 2022 compared to a net loss of $21.2 million for the three months ended December 31, 2021 and $75.7 million for the year ended December 31, 2021. This decrease was primarily due to a decrease in research and development expenses.

Conference call: HOOKIPA will host a conference call and live webcast at 8:30 am EDT today to discuss its financial results and provide a corporate update.

Dial In:+1 800-715-9871

UK Dial In:0800 260-6466

Austria Dial In:+43 800 070441

Conference ID:7669853

The webcast and the presentation will be available within the Investors & Media section of HOOKIPA's website at https://ir.hookipapharma.com/events. An archived replay will be accessible for 30 days following the event.

HOOKIPA Pharma Inc. (NASDAQ: HOOK) is a clinical-stage biopharmaceutical company focused on developing novel immunotherapies, based on its proprietary arenavirus platform, which are designed to mobilize and amplify targeted T cells and thereby fight or prevent serious disease. HOOKIPA's replicating and non-replicating technologies are engineered to induce robust and durable antigen-specific CD8+ T cell responses and pathogen-neutralizing antibodies. HOOKIPA's pipeline includes its wholly owned investigational arenaviral immunotherapies targeting Human Papillomavirus 16-positive cancers, prostate cancers, and other undisclosed oncology programs. HOOKIPA is collaborating with Roche on an arenaviral immunotherapeutic for KRAS-mutated cancers. In addition, HOOKIPA aims to develop functional cures of HBV and HIV in collaboration with Gilead.

Find out more about HOOKIPA online at www.hookipapharma.com.

HOOKIPA Forward Looking Statements

Certain statements set forth in this press release constitute "forward-looking" statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended. Forward-looking statements can be identified by terms such as "believes," "expects," "plans," "potential," "would" or similar expressions and the negative of those terms. Such forward-looking statements involve substantial risks and uncertainties that could cause HOOKIPA's research and clinical development programs, future results, performance or achievements to differ significantly from those expressed or implied by the forward-looking statements. Such risks and uncertainties include, among others, the uncertainties inherent in the drug development process, including HOOKIPA's programs' early stage of development, the process of designing and conducting preclinical and clinical trials, the regulatory approval processes, the timing of regulatory filings, the challenges associated with manufacturing drug products, HOOKIPA's ability to successfully establish, protect and defend its intellectual property, risks relating to business interruptions resulting from the coronavirus (COVID-19) disease outbreak or similar public health crises, the impact of COVID-19 on the enrollment of patients and timing of clinical results, and other matters that could affect the sufficiency of existing cash to fund operations. HOOKIPA undertakes no obligation to update or revise any forward-looking statements. For a further description of the risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to the business of the company in general, see HOOKIPA's annual report on Form 10-K for the year ended December 31, 2022, which is available on the Security and Exchange Commission's website at www.sec.gov and HOOKIPA's website at www.hookipapharma.com.

Investors and others should note that we announce material financial information to our investors using our investor relations website (https://ir.hookipapharma.com/), SEC filings, press releases, public conference calls and webcasts. We use these channels, as well as social media, to communicate with our members and the public about our company, our services and other issues. It is possible that the information we post on social media could be deemed to be material information. Therefore, we encourage investors, the media, and others interested in our company to review the information we post on the U.S. social media channels listed on our investor relations website.

Consolidated Statements of Operations (Unaudited)

(In thousands, except share and per share data)

Condensed Balance Sheets

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