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.”