AbCellera's ABCL635 Hits Phase 2 Primary Endpoints for Hot Flash Treatment With Single Dose

AbCellera Biologics (NASDAQ: ABCL) announced positive top-line Phase 2 results for ABCL635, its investigational NK3 receptor antagonist antibody targeting moderate-to-severe vasomotor symptoms, commonly known as hot flashes, due to menopause. The randomized, double-blind, placebo-controlled study met both primary efficacy endpoints at week 4 following a single subcutaneous 600 mg dose. Shares of ABCL gained 34.78% on Monday, August 10, while the S&P 500 was essentially flat, declining 0.03%.

Phase 2 Trial Results

• Frequency reduction: ABCL635 produced a mean reduction of 8.8 moderate-to-severe vasomotor symptom events per day from baseline at week 4, versus 3.5 for placebo, a mean placebo-adjusted treatment difference of 5.3 (p<0.001). The mean percent reduction was 83% for ABCL635 versus 33% for placebo, a placebo-adjusted difference of 50%.
• Severity reduction: ABCL635 reduced severity scores by a mean of 1.4 points at week 4 versus 0.3 for placebo, a placebo-adjusted difference of 1.1 (p<0.001). The mean percent reduction in severity was 58% versus 12% for placebo, a placebo-adjusted difference of 46%.
• Trial design: 92 postmenopausal women were enrolled, experiencing a mean of approximately 10 moderate or severe hot flashes per day, randomized 1:1 to ABCL635 or placebo.
• Secondary endpoints: ABCL635 also produced meaningful improvements in patient sleep scores and patient global impression of change (PGI-C).
• Tolerability: No serious adverse events, severe adverse events, or adverse events leading to study discontinuation were reported. The most common adverse events exceeding placebo rates were headache, fatigue, and injection site reaction.

Why It Matters

ABCL635 specifically targets the neurokinin 3 receptor (NK3R), a G protein-coupled receptor expressed on KNDy neurons in the hypothalamus, representing AbCellera's first GPCR and ion channel platform program to advance into the clinic, having entered Phase 1 in July 2025. The Phase 2 data establish ABCL635 as a non-hormonal, long-acting option delivered via a single subcutaneous injection, a dosing profile distinct from currently available daily oral treatments. According to the company's press release, statistical significance was maintained from week 1 through week 4 across both frequency and severity measures.

Dr. JoAnn V. Pinkerton, Women's Midlife Professor of Obstetrics and Gynecology at the University of Virginia School of Medicine, stated in the press release: "The four-week data for the Phase 2 study of ABCL635 demonstrate a new efficacy benchmark for the reduction of hot flashes both in frequency and severity, as well as improvements in sleep. If validated in Phase 3, ABCL635 could offer a new treatment option with a more convenient dosing regimen and potentially less toxicity." The company estimates more than 12 million women in the US experience moderate-to-severe vasomotor symptoms, of which more than six million seek treatment.

Wall Street View

Analyst sentiment on ABCL was already tilted constructively heading into this readout. The company held a conference call and live webcast at 7:30 a.m. ET on Monday to discuss the results with investors and analysts.

Investor Takeaway

The Phase 2 data provide AbCellera with a primary-source clinical foundation to advance ABCL635 toward Phase 3 planning, with the single-dose subcutaneous design potentially differentiating it from existing daily oral NK3R antagonists in the vasomotor symptom market. The favorable tolerability profile, absence of serious adverse events across the four-week period, and sustained statistical significance from week 1 through week 4 reduce a key de-risking hurdle ahead of a larger, longer Phase 3 study. Investors will now look to management for clarity on Phase 3 trial design, timeline, and capital requirements given the company currently carries $505 million in cash against an ongoing net loss profile.