Atreca Presents Data from Ongoing Phase 1b Study of ATRC-101 in Patients with Select Advanced Solid Tumors during Oral Abstract Session at the ASCO 2023 Annual Meeting

Clinical activity observed in multiple tumor types; longer progression-free survival observed in patients with high target expression; ATRC-101 continues to be well-tolerated

Phase 2 go/no-go decisions for ATRC-101 expected by end-of-year

SAN CARLOS, Calif., June 05, 2023 (GLOBE NEWSWIRE) -- Atreca, Inc. (Atreca) (NASDAQ:BCEL), a clinical-stage biotechnology company focused on developing novel therapeutics generated through a unique discovery platform based on interrogation of the active human immune response, announced that Dr. Bartosz Chmielowski, Health Sciences Clinical Professor of Medicine in the Division of Hematology-Oncology at the University of California Los Angeles, presented safety and efficacy data from the ongoing Phase 1b study of ATRC-101 in patients with select advanced solid tumors cancer during an oral abstract session on Sunday, June 4 at the American Society of Clinical Oncology (ASCO) 2023 Annual Meeting. The presentation provided a summary of clinical data collected as of a February 17, 2023, data cut-off date.

"We are pleased to be able to present these results in an oral presentation at ASCO, which validate the potential of our discovery platform and its ability to identify promising therapeutic antibodies against novel tumor targets," said Dr. Philippe Bishop, Chief Medical Officer of Atreca. "We are continuing to enroll subjects in both the Q3W monotherapy and combination therapy cohorts at the 30 mg/kg dose level, with a focus on the recruitment of H-score high participants across tumor types. The additional data we generate in the coming months will be important in informing our go/no-go decisions for indication-specific Phase 2 development expected later this year."

• As of the data cut-off date of February 17, 71 participants had been dosed in the trial and evaluated for safety, with 62 participants receiving either the 3, 10 or 30 mg/kg dose including 42 participants receiving ATRC-101 monotherapy every 3 weeks (Q3W), 11 receiving ATRC-101 monotherapy every 2 weeks (Q2W), and 9 receiving a combination of ATRC-101 and pembrolizumab. Participants enrolled in the study had received a median of five prior lines of treatment.
  • ATRC-101 has been generally well-tolerated. Treatment emergent adverse events of Grade ≥3 occurred in 27 (38%) participants and were deemed related to ATRC-101 in 2 (3%). None led to treatment discontinuation or dose reduction due to ATRC-101.

• Atreca continued to observe that high target expression (as defined by an H-score ≥50) discriminates for anti-tumor activity in the 3, 10 and 30 mg/kg dose cohorts.
  • Among the 17 participants with a high target expression at screening treated with monotherapy at the higher dose levels, disease control was observed in 59% (10 of 17 patients) including 9 (53%) patients with stable disease (SD) and one (6%) patient with a partial response (PR).
  • With combination patients included (n=24), disease control was observed in 14 (58%) including 12 (50%) SD, 1 (4%) PR and 1 (4%) CR.

• Longer progression-free survival was observed in patients with high target expression treated in the 3, 10 and 30 mg/kg dose cohorts.
  • A hazard ratio of 0.47 was observed in a Kaplan Meier analysis of monotherapy patients treated at the higher dose levels separated by H-score (n=41)
  • A hazard ratio of 0.40 was observed in the Kaplan Meier analysis of combination therapy patients separated by H-score (n=49).

"These data continue to support ATRC-101's observed safety and tolerability profile, and the correlation between longer progression-free survival and high target expression," added Dr. Bartosz Chmielowski, Professor of Medicine at the University of California Los Angeles. "More importantly, ATRC-101 demonstrated durable disease control among heavily pre-treated patients across a range of tumor types. Based on these data, I believe ATRC-101 has the potential address a significant unmet need in multiple tumor types as a part of a range of potential therapeutic combinations with established regimens, including checkpoint inhibitors."

About Atreca, Inc.

Atreca is a biopharmaceutical company developing novel antibody-based immunotherapeutics generated by its differentiated discovery platform. Atreca's platform allows access to an unexplored landscape in oncology through the identification of unique antibody-target pairs generated by the human immune system during an active immune response against tumors. These antibodies provide the basis for first-in-class therapeutic candidates, such as our lead product candidate ATRC-101. A Phase 1b study evaluating ATRC-101 in multiple solid tumor cancers is currently enrolling patients. For more information on Atreca, please visit www.atreca.com.

Forward-Looking Statements

This release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These forward-looking statements include without limitation those regarding our strategy and future plans, including statements regarding the continuing safety and tolerability of ATRC-101 in our ongoing Phase 1b trial, enrollment of patients in our Phase 1b clinical trial of ATRC-101, our belief that our ATRC-101 results validate the potential of our discovery platform and its ability to identify promising therapeutic antibodies against novel tumor targets, our plan to make go/no-go decisions by the end of 2023 for potential Phase 2 development of ATRC-101, the development of ATRC-101 and our clinical and regulatory plans, and the timing thereof, data read-outs and the timing thereof, including the reporting of updated data from the monotherapy and pembrolizumab combination arms of our Phase 1b clinical trial of ATRC-101, the continuing correlation between longer progression-free survival and high target expression in our Phase 1b clinical trial of ATRC-101, and the potential of ATRC-101 to address a significant unmet need in multiple tumor types as a part of a range of potential therapeutic combinations with established regimens, including checkpoint inhibitors. These forward-looking statements include, but are not limited to, statements about our plans, objectives, representations and contentions and are not historical facts and typically are identified by use of terms such as "continue," "will," "expect," "advance," "target," "belief," and similar words, although some forward-looking statements are expressed differently. Our actual results may differ materially from those indicated in these forward-looking statements due to risks and uncertainties related to the initiation, timing, progress and results of our research and development programs, preclinical studies, clinical trials, regulatory submissions, and other matters that are described in our most recent Annual Report on Form 10-K and Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (SEC) and available on the SEC's website at www.sec.gov, including the risk factors set forth therein. Investors are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this release, and we undertake no obligation to update any forward-looking statement in this press release, except as required by law.

Contacts

Atreca, Inc.

Herb Cross

Chief Financial Officer

[email protected]

Investors:

Alex Gray, 650-779-9251

[email protected]

Media:

Julia Fuller, 858-692-2001

[email protected]