Adicet Bio Highlights ADI-001 Expansion, Persistence and Pharmacodynamic Profile from Ongoing Phase 1 Study at the 65th American Society of Hematology (ASH) Annual Meeting

Adicet Bio, Inc. (Nasdaq: ACET), a clinical stage biotechnology company discovering and developing allogeneic gamma delta T cell therapies for cancer, today announced that an abstract outlining PK and PD profiling data from the Company's ongoing Phase 1 study of ADI-001 for the potential treatment of relapsed or refractory aggressive B-cell NHL was made available as part of the 65^th ASH Annual Meeting, being held December 9-12, 2023 in San Diego, California. The data will be provided during a poster presentation at the ASH Annual Meeting on Sunday, December 10, 2023.

"We are pleased to share encouraging observations from the pharmacokinetic and pharmacodynamic analyses of ADI-001 at ASH, further characterizing its potential as a best-in-class allogeneic CAR T platform. The data presented today showed dose-dependent expansion and persistence that met or exceeded that in prescribing information of approved autologous CD19 CAR T therapies, supporting ADI-001's potential as an effective therapeutic option for patients with advanced cancers," said Francesco Galimi, M.D., Ph.D., Chief Medical Officer. "Historically, expansion and persistence of cell therapy products and release of functional cytokines have correlated with patient outcomes. We remain on track to provide a clinical update from the Phase 1 study in NHL patients in the second half of 2024."

Data highlights included in the ASH presentation were as follows:

• Robust dose-dependent expansion and persistence of ADI-001 were observed using three different methodologies for measuring exposure.
• ADI-001 displayed a strong exposure profile and was positively associated with both PD correlates and clinical response, as supported by the following:
  • At DL3 and DL4, ADI-001 Cmax and Tmax that met or exceeded that in prescribing information of approved autologous CD19 CAR T therapies.
  • Increasing dose levels showed higher Cmax and AUC and were associated with patient clinical responses.
  • ADI-001 stimulation and proliferation were associated with peak levels of CAR+ cells and higher production of polyfunctional cytokines, particularly in patients whose best overall response was complete response or partial response.
  • Elevating levels of endogenous cytokines, comprising stem cell factor and IL-15, may potentially contribute to increased ADI-001 expansion and clinical response.
  • ADI-001 exposure or clinical response showed no correlation with the degree of shared HLA alleles between patient and ADI-001.

Details of the poster presentation are as follows:

• Title: Expansion, Persistence and Pharmacodynamic Profile of ADI-001, a First-in-Class Allogeneic CD20-Targeted CAR Gamma Delta T Cell Therapy, in Patients with Relapsed/Refractory Aggressive B-Cell Non-Hodgkin's Lymphoma
• Poster Number: 3478
• Session Name: 704. Cellular Immunotherapies: Early Phase and Investigational Therapies: Poster II
• Presenting Author: Monica Moreno, Ph.D.
• Date/Time: Sunday, December 10, 2023, from 6:00 - 8:00 p.m. PST

About ADI-001

ADI-001 is an investigational allogeneic gamma delta CAR T cell therapy being developed as a potential treatment for relapsed or refractory B-cell NHL. ADI-001 targets malignant B-cells via an anti-CD20 CAR and via the gamma delta innate and T cell endogenous cytotoxicity receptors. Gamma delta T cells engineered with an anti-CD20 CAR have demonstrated potent antitumor activity in preclinical models, leading to long-term control of tumor growth. ADI-001 was granted Fast Track Designation by the U.S. Food and Drug Administration (FDA) for the potential treatment of relapsed or refractory B-cell NHL.

About the GLEAN Study

The Phase 1 study is an open-label, multi-center study of ADI-001 enrolling adults diagnosed with B-cell malignancies who have either relapsed, or are refractory to, at least two prior regimens. The primary objectives of the study are to evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of ADI-001, and to determine optimal dosing as a monotherapy. For more information about the clinical study design, please visit www.clinicaltrials.gov (NCT04735471).

About Adicet Bio, Inc.

Adicet Bio, Inc. is a clinical stage biotechnology company discovering and developing allogeneic gamma delta T cell therapies for cancer. Adicet is advancing a pipeline of "off-the-shelf" gamma delta T cells, engineered with chimeric antigen receptors (CARs) to enhance selective tumor targeting and facilitate innate and adaptive anti-tumor immune response for durable activity in patients. For more information, please visit our website at https://www.adicetbio.com.

Forward-Looking Statements

This press release contains "forward-looking statements" of Adicet within the meaning of the Private Securities Litigation Reform Act of 1995 relating to business and operations of Adicet. The words "anticipate," "believe," "continue," "could," "estimate," "expect," "intend," "may," "plan," "potential," "predict," "project," "should," "target," "would" and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. These forward-looking statements include, but are not limited to, express or implied statements regarding: preclinical and clinical development of Adicet's product candidates, including future plans or expectations for ADI-001, the potential safety, durability, tolerability and efficacy of ADI-001; the potential of Adicet's allogenic CAR T cell platform to be best-in-class; and the expected progress, timing and success of the Phase 1 study of ADI-001 in relapsed/refractory B-cell NHL patients, including expectations around a clinical update in the second half of 2024. Any forward-looking statements in this press release are based on management's current expectations and beliefs of future events, and are subject to a number of risks and uncertainties that could cause actual results to differ materially and adversely from those set forth in or implied by such forward-looking statements, including without limitation, the effect of global economic conditions and public health emergencies on Adicet's business and financial results, including with respect to disruptions to our preclinical and clinical studies, business operations, employee hiring and retention, and ability to raise additional capital; Adicet's ability to execute on its strategy including obtaining the requisite regulatory approvals on the expected timeline, if at all; that positive results, including interim results, from a preclinical or clinical study may not necessarily be predictive of the results of future or ongoing studies; clinical studies may fail to demonstrate adequate safety and efficacy of Adicet's product candidates, which would prevent, delay, or limit the scope of regulatory approval and commercialization; and regulatory approval processes of the FDA and comparable foreign regulatory authorities are lengthy, time-consuming, and inherently unpredictable; and Adicet's ability to meet production and product release expectations. For a discussion of these and other risks and uncertainties, and other important factors, any of which could cause Adicet's actual results to differ from those contained in the forward-looking statements, see the section entitled "Risk Factors" in Adicet's most recent annual report on Form 10-K and our periodic reports on Form 10-Q and Form 8-K filed with the SEC, as well as discussions of potential risks, uncertainties, and other important factors in Adicet's other filings with the SEC. All information in this press release is as of the date of the release, and Adicet undertakes no duty to update this information unless required by law.