Phase 2 deja vu for gossamer bio after ulcerative colitis med flops

Gossamer bio will end the extension of a phase 2 study for a small molecule ulcerative colitis med that was found to be ineffective—the second time in 18 months the company has seen a top program fail a midstage trial.

The drug, GB004, did not significantly improve remission rates for either of two open-label and treat-through extension dose arms of the trial at 12 weeks compared to placebo, the company announced Monday. There were also no meaningful improvements identified in histologic or mucosal healing. 

The phase 2 study enrolled 236 patients with mild-to-moderate UC that had yet to be treated with other approved meds for the condition. GB004 was given in addition to 5-aminosalicylate background therapy with or without systemic steroids. The drug was generally tolerable with mostly mild adverse events, although the treatment arm had higher incidences than the placebo arm.

On an investor call Monday, gossamer’s chief medical officer Richard Aranda, M.D., said the totality of the evidence suggested the drug’s mechanism ultimately may not have been a good fit for the disease.

“While there were some numeric, maybe, differences in the high dose compared to the low dose, I think the totality of the data not hitting any primary or secondary endpoints tell us that the mechanism is just not adequate enough to be sufficient to treat a disease such as ulcerative colitis,” he said. 

In light of the data, the company is winding down the extensions of the study. Gossamer leaders did not indicate whether or not they would spike the program altogether or pursue other indications. 

It’s another phase 2 setback for the San Diego biotech after a previous asset, GB001, failed in two midphase trials back in October 2020 for two different indications, chronic rhinosinusitis and asthma. The company ended the chronic rhinosinusitis pathway as a result but felt enough positive data came from the asthma trial to continue development, although it sought a partner to help fund a phase 3 trial. 

Naturally, gossamer is now turning to other assets, particularly seralutinib which is also in phase 2 for pulmonary arterial hypertension. Topline data from that study is expected in the fourth quarter of 2022. The company is also optimistic about an earlier asset in phase 1, GB 5121, for patients with central nervous system lymphoma, which it believes has the potential to nab accelerated approval from the FDA pending phase 2 success. Gossamer said some preliminary data from a phase 1 program could be available by the end of the year.

To see out these programs, gossamer will be relying on its still sizable $272 million cash pile. On the investor call, executives said that money should last until late 2023, or the first quarter of 2024 to enable a phase 2 readout of seralutinib in addition to underwriting “substantial momentum in 5121.” 

In light of the news, the company’s shares took a tumble, falling more than $1.50 per share to $7.12, a nearly 20% dive. Regardless, analysts from SVB Securities believe that the failure was a "clearing event" ahead of the company's looming readouts and they were bullish on its prospects.