• Recommended dose selected for evaluation of anti-tumor activity in the ongoing Phase 2a portion of the Phase 1/2a study

23andMe Holding Co. (Nasdaq: ME) (23andMe), a leading human genetics and biopharmaceutical company, announced results from the Phase 1 portion of its Phase 1/2a study evaluating 23ME-00610, an investigational antibody targeting CD200R1. 23ME-00610 demonstrated an acceptable safety and tolerability profile, with favorable pharmacokinetics (PK) and peripheral saturation of the CD200R1 target. Based on the Phase 1 data, a dose of 23ME-00610 given at 1400 mg intravenously every 3 weeks was selected for evaluation of anti-tumor activity in the ongoing Phase 2a portion of the Phase 1/2a (Phase 2a) 23ME-00610 study.

23andMe plans to present these data at the American Association for Cancer Research (AACR) Annual Meeting 2023 in Orlando, Florida on April 18, 2023, from 9:00 AM - 12:30 PM ET (poster section 45, #CT174). The poster presentation will be available on the 23andMe Therapeutics and Investor websites at 9:00 AM ET on April 18, 2023, and will contain updated data obtained after the abstract submission cut-off date. The abstract that was released today is available on the AACR website.

“We are pleased to present the first clinical data from a wholly-owned asset in our immuno-oncology portfolio. Data from the Phase 1 portion of our 23ME-00610 study included an acceptable safety profile along with saturation of the intended target, and support 23ME-00610’s further development in patients with advanced cancer,” said Jennifer Low, MD, PhD, Head of Therapeutics Development at 23andMe. “The Phase 2a portion of the study is now underway and we look forward to further evaluation of 23ME-00610 in the trial’s expansion cohorts.”

23ME-00610 Phase 1 Results:
Participants with histologically diagnosed locally advanced (unresectable), or metastatic carcinoma or sarcoma who progressed on standard therapies with an Eastern Cooperative Oncology Group (ECOG) score of 0 or 1 were enrolled across the 2 mg to 1400 mg cohorts. Participants received 23ME-00610 intravenously every 3 weeks (Q3W) infused over 30 minutes.

Key results from the study include:

• No dose limiting toxicities were observed. Among study participants, most experienced at least 1 treatment related adverse event (TRAE); the majority were Grade 1 or 2.
• Investigator-assessed immune-related AEs including hypothyroidism, pruritis, fatigue and chills were observed at higher pharmacologically relevant dose levels (doses 60 mg and above).
• The PK of 23ME-00610 were dose-proportional at doses 60 mg and above, with a median terminal half-life of ~12 days at 1400 mg, supporting administration of 23ME-00610 every three weeks.
• Peripheral saturation of CD200R1 was observed at doses 60 mg and above, as measured by receptor occupancy on T cells and neutrophils, and levels of free soluble CD200R1.

A RP2D of 1400 mg 23ME-00610 was selected for evaluation in the Phase 2a portion of the study.

23ME-00610 Phase 2a:
The Phase 2a portion of the Phase 1/2a study is currently underway, evaluating the anti-tumor activity of the 23ME-00610 monotherapy in a number of expansion cohorts, and further characterizing the safety, tolerability, PK and PD profile of 23ME-00610. The Phase 2a portion will include assessment of objective response rate (ORR), progression-free survival (PFS) and overall survival (OS) in the expansion cohorts.

The expansion cohorts will enroll patients with clear cell renal cell carcinoma; epithelial ovarian, fallopian tube or primary peritoneal carcinoma; neuroendocrine cancers; small cell lung cancer; and microsatellite instability-high (MSI-H) or tumor mutational burden-high (TMB-H) cancers that have progressed on standard therapies. A cohort of adolescents with locally advanced unresectable, or metastatic solid malignancies will also be enrolled.