Corbus reports 5 percent weight loss for oral CB1 pill CRB-913 in Phase 1b trial

Corbus Pharmaceuticals reported on September 14 that its experimental once-daily oral drug CRB-913 produced an average weight loss of 5.0 percent at 12 weeks at the highest dose tested, compared with 0.0 percent for placebo, in a Phase 1b trial in adults with obesity ^[1][2].

The trial, called CANYON-1, was a 16-week double-blind, placebo-controlled, dose-ranging study that enrolled 254 adults with obesity who did not have diabetes, at 15 sites in the United States (NCT07310901) ^[1]. Participants were randomly assigned to placebo (66 people) or to CRB-913 at 20 mg (65), 40 mg (61) or 60 mg (62). Everyone assigned to the drug started at 20 mg per day and increased the dose every two weeks until reaching their assigned level. They took the drug for 12 weeks and were followed for another four ^[1].

Average weight loss was 2.8 percent at 20 mg, 3.3 percent at 40 mg and 5.0 percent at 60 mg. All three results were statistically significant compared with placebo, with p-values below 0.0001, and the company said there was no sign that weight loss had leveled off at any dose by week 12 ^[1][2]. In the 60 mg group, everyone who completed the study lost some weight, 44.4 percent lost at least 5.0 percent of their starting weight, and 6.7 percent lost more than 7.5 percent. The largest weight loss recorded in that group was 13.4 percent ^[1].

Corbus said CRB-913 was generally safe and well tolerated. Rates of stopping treatment because of side effects ranged from 3.1 percent to 13.1 percent across the CRB-913 groups ^[1]. The company compared that with published figures of 6.9 percent to 20.7 percent for approved oral GLP-1 drugs, and 13 percent to 42 percent reported for monlunabant, another experimental drug in the same CB1 class. Corbus also said gastrointestinal side effects appeared lower than those of marketed oral GLP-1s, based on comparisons across separate trials rather than head-to-head testing ^[1]. RTTNews reported that psychiatric side effects were broadly in line with GLP-1 drugs ^[2].

CRB-913 is a CB1 inverse agonist designed to act mostly outside the brain. Earlier CB1 drugs were withdrawn from the market because of neuropsychiatric harm, and Corbus is betting that keeping the drug out of the brain avoids those problems ^[2]. RTTNews reported that investigators saw no depressive effects of the kind linked to the older, brain-acting CB1 agents ^[2]. "These results confirm our core hypothesis," chief executive Yuval Cohen said, adding that the company is preparing to move CRB-913 into Phase 2 development ^[2].

Why it matters for patients

CRB-913 is not approved, and these are early results from a small, 12-week study. A 5 percent average weight loss is a modest change, and the trial did not compare the pill with semaglutide (Ozempic, Wegovy, Rybelsus), tirzepatide (Mounjaro, Zepbound) or any approved obesity medicine. How CRB-913 stacks up against those treatments has not been tested and is not known.

What makes it notable is the mechanism. Semaglutide, tirzepatide and orforglipron (Foundayo) all work through incretin hormones. CRB-913 does not. That could matter to the many patients who cannot tolerate GLP-1 side effects or do not lose enough weight on them; RTTNews noted that more than 60 percent of people stop obesity treatment within the first year ^[2].

Safety over longer use is the open question for this drug class. The CANYON-1 study ran 12 weeks of dosing with four weeks of follow-up, and results from that follow-up period have not been reported. Whether psychiatric or other side effects appear with longer treatment or higher doses will not be clear until larger and longer trials are run.

What happens next

Corbus said the full CANYON-1 data will be presented in a late-breaking session at ObesityWeek 2026 on November 14, 2026 ^[1][2]. The company expects to start a Phase 2 monotherapy study in the first half of 2027 and is also looking at combining CRB-913 with a GLP-1 drug ^[2]. A Phase 2 program typically takes years, so any possible approval is well beyond that. Corbus shares closed at $8.12 on September 11 and traded at $9.75 in pre-market trading on September 14, up about 20 percent ^[2].