HOOKIPA advances HB-200 program to Phase 2 and prioritizes oncology portfolio based on clinical data updates across its novel arenaviral platform Based on positive interim Phase 1 data, HOOKIPA initiates Phase 2 study to

HOOKIPA advances HB-200 program to Phase 2

and prioritizes oncology portfolio based on clinical data updates across its novel arenaviral platform

York, US and Vienna, Austria, November 9, 2021 - HOOKIPA Pharma Inc. (NASDAQ: HOOK,

HOOKIPA'), a company developing a new class of immunotherapeutics based on its proprietary arenavirus platform, announced

it is advancing HB-201 to Phase 2, to be evaluated in combination with pembrolizumab as 1st-

or 2nd-line treatment for Human Papillomavirus Positive 16 (HPV16+) squamous cell head

and neck cancers (HNSCC). Interim Phase 1 data in heavily pre-treated patients continue to show HB-200 monotherapy (both HB-201 alone

and HB-202/HB-201) is highly effective at expanding T cells, has a favorable tolerability profile and promising, early anti-tumor activity.

As of November 1, 2021, among 28 patients dosed intravenously, HB-200 resulted in a 75 percent disease control rate and shrinkage of

target lesions in 53 percent of patients. In these patients, HOOKIPA has observed three partial responses (including one confirmed and

one unconfirmed in an ongoing patient) and one ongoing patient with a near partial response (29 percent tumor shrinkage). Based on the

strength of the HB-200 data, HOOKIPA has prioritized its oncology portfolio and plans further development of its infectious disease programs

to be done in partnership with other companies. HOOKIPA will host an investor conference call to review the data at 4:30 p.m. ET.

"We are incredibly excited about our Phase

1 HB-200 data, especially the demonstrated tumor-specific T cell responses and tumor shrinkage in heavily pre-treated HNSCC patients,

which we believe are highly differentiated from other active immunization technologies," said Joern Aldag, Chief Executive Officer

at HOOKIPA. "Based on these data, we're excited to advance our promising HB-200 program into Phase 2, initially with the HB-201

and pembrolizumab combination for head and neck cancer patients, while accelerating the development of our earlier stage immuno-oncology

candidates HB-300 and HB-700 in prostate and KRAS-mutated cancers, respectively, and focusing our efforts on exploring the potential of

our novel arenaviral technology to address unmet needs in cancer."

Interim data from the ongoing Phase 1 dose

escalation study (NCT04180215) show that HB-200 (either as HB-201 or as alternating two-vector HB-202/HB-201) rapidly induces high

levels of tumor-specific CD8+ T cells considered to be predictive of response, with a favorable tolerability profile and promising,

early anti-tumor activity in heavily pre-treated HPV16+ HNSCC cancer patients.

As of the November 1, 2021 data cut-off, 62 patients

(representing 24 new patients since the data presented at the American Society of Clinical Oncology in June 2021) with advanced HPV16+

tumors were enrolled and received HB-200 therapy. Forty patients with HNSCC tumors were treated intravenously every three weeks, including

20 patients who received single vector HB-201 and 20 patients who received alternating two-vector HB-202/HB-201. The other 22 patients

had either other HPV16+ tumor types (not HNSCC) and/or received different HB-200 regimens. Participants received a median of three prior

therapies (ranging from zero to 11), and 87 percent had previously received a checkpoint inhibitor regimen. The following safety and interim

efficacy data reflect the November 1 cut-off date.

HB-200 continued to demonstrate a favorable tolerability

profile in heavily pre-treated patients with HPV16+ cancers, highlighting its potential in possible combination with checkpoint inhibitors

and other agents. Treatment-related adverse events were reported in 66 percent of 62 evaluable patients, with only 8 percent experiencing

treatment-related adverse events rated grade 3 or higher.

promising, early anti-tumor activity in the 28 evaluable patients with advanced HNSCC. Specifically:

compare favorably to the standard of care treatments nivolumab and pembrolizumab used in a 2nd plus-line setting in PD1-inhibitor na ve

HNSCC patients. Based on peer-reviewed published data, nivolumab showed a mPFS of 2 months1

whereas pembrolizumab had disease control rates of 35 percent overall and 40 percent in the HPV+ subset in the 2nd plus-line

continued to show that HB-200 rapidly induces high levels of activated, tumor-specific CD8+ T cells. As of the September 1, 2021 data

cut-off, 20 patients were evaluable, including 10 patients who received HB-201 and 10 who received alternating two-vector HB-202/HB-201.

The analysis showed:

Ferris R et al. Nivolumab for recurrent squamous-cell carcinoma of the head and neck. N Engl J Med. 2016; 375:1856-1867.

Mehra R et al. Efficacy and safety of pembrolizumab in recurrent/metastatic head and neck squamous cell carcinoma: pooled analysis after

long-term follow up in KEYNOTE-012. British J of Cancer. 2018; 119:153-159.

of published literature, we believe that no other active immunization approach has demonstrated these types of results, which highlight

the magnitude of tumor-specific CD8+ T cells induced by HB-200 therapy as well as the potential for HOOKIPA's versatile arenaviral

platform to enhance anti-tumor activity across tumor killing mechanisms.

these T cell data are preliminary, it's clear that HB-200 induces a rapid

and robust vaccine-specific T cell response at magnitudes that we as a field have theorized would result in efficacy, if such levels were

ever achieved," said Dmitriy Zamarin, MD, PhD, Translational Research Director in Gynecologic Medical Oncology at Memorial Sloan

Kettering Cancer Center (MSK) and co-investigator in this study. "Hookipa's arenavirus vectors are, for the first time, generating

these levels and, with that, we are seeing monotherapy efficacy in patients with advanced heavily-pretreated cancers."

Oncology pipeline expansion

There is considerable unmet need in head and neck

cancers, and the HB-200 program represents broad potential for additive benefits in combination with current standard of care and novel

agents to improve anti-tumor immune response in these patients. HOOKIPA has initiated the Phase 2 expansion portion of its ongoing HB-200

study to evaluate HB-201 in combination with pembrolizumab in 1st- and 2nd-line

The company also plans to initiate a separate,

randomized Phase 2 study of HB-200 in combination with pembrolizumab as part of its clinical collaboration with Merck & Co., Inc.,

Kenilworth, NJ, USA.

Based on the positive HB-200 data to-date, HOOKIPA

is focusing future research and development in oncology, advancing efforts in head and neck cancer with HB-200 and prostate cancers with

HB-300, as well as expanding its pipeline to include HB-700, a new program targeting KRAS-mutated colorectal, pancreatic and lung cancers.

Infectious disease portfolio update

Updated interim data from the ongoing Phase 2

clinical trial (NCT03629080) of HB-101, a prophylactic Cytomegalovirus (CMV) vaccine candidate, show strong immunogenicity and reduced

incidence of CMV viremia in people who received three doses of HB-101, consistent with results previously reported in November 2020. Compared

to placebo, participants vaccinated with three HB-101 doses prior to kidney transplant had:

While there were two cases of CMV disease reported

in the placebo group in November 2020, these cases have since been re-classified as not CMV disease.

Safety and tolerability were evaluated in 80

participants who were enrolled in the trial by the cut-off date of July 30, 2021. HB-101 was generally well tolerated with 21 percent

of HB-101 recipients experiencing side effects related to vaccine administration. A total of five cases of human leukocyte antigen (HLA)-sensitization

have been reported, four characterized as serious adverse events.

Enrollment closed in June 2021 with 80

patients enrolled, and participants will continue to be monitored for the 12-month observation period following kidney transplantation.

Final results are anticipated in 2023. With no approved CMV vaccine, there remains considerable unmet need for people with solid organ

transplants. HOOKIPA will explore partnership opportunities for further development of HB-101 in order to focus on advancing its promising

HOOKIPA is progressing its research collaboration

with Gilead to develop a potential functional cure for Hepatitis B virus (HBV). The HBV program successfully passed Gilead's Request

for Development milestone, and Gilead plans to progress the program into IND-enabling stage in 2022 to support IND filing for the arenavirus

vector combination. For the HIV program, after HOOKIPA successfully completed all pre-clinical research obligations in accordance

with the mutual Collaboration Agreement, Gilead informed HOOKIPA of their intention not to move forward with this program according to

current terms. HOOKIPA is in ongoing discussions with Gilead regarding a revised Collaboration Agreement.

HOOKIPA will host an investor conference call

to review the data at 4:30 p.m. ET.

A live webcast of the call can be accessed on

HOOKIPA's website at www.hookipapharma.com/events. An archived webcast will be available for 30 days on the Events webpage.

HB-201 and HB-202 are HOOKIPA's lead oncology

candidates engineered with the company's proprietary replicating arenaviral vector platform. Each single-vector compound uses a

different arenavirus backbone (Lymphocytic Choriomeningitis Virus for HB-201 and Pichinde

Virus for HB-202), while expressing the same antigen, an E7E6 fusion protein derived from HPV16. In pre-clinical studies, alternating

administration of HB-201 and HB-202 resulted in a ten-fold increase in immune response and better disease control than either compound

alone. HB-201 is being tested clinically as a single vector therapy and also in an alternating vector combination with HB-202.

About the HB-200 trial (NCT04180215)

This Phase 1/2 clinical trial is an open-label

trial exploring different dose levels and dosing schedules in individuals with treatment-refractory HPV16+ head and neck cancers who

progressed on standard of care, including check point inhibitors. The trial is evaluating HB-201 as a monotherapy, as an alternating