Insmed Stock Slides After Brensocatib Nasal Polyp Trial Fails
The development setback for a secondary indication tempers pipeline hopes, even as the company pivots with a new cancer drug acquisition.
Shares of Insmed (NASDAQ: INSM) fell sharply after the biopharmaceutical company announced it was terminating the development of its key drug, brensocatib, for the treatment of chronic rhinosinusitis without nasal polyps (CRSsNP).
The decision came after the drug failed to meet its primary endpoint in a mid-stage clinical trial, a significant setback for the company’s plans to expand the drug’s applications. Concurrent with the news, Insmed also revealed a strategic move into oncology, acquiring the rights to the cancer therapy tislelizumab from BeiGene.
Insmed’s Phase 2b BiRCh study, which enrolled 288 patients, did not show a statistically significant improvement in symptoms for patients taking brensocatib compared to those on a placebo. According to a company statement, the trial failed to meet its primary goal, which measured the change in a composite score of sinus symptoms at 24 weeks. As a result, the CRSsNP development program has been discontinued.
"While we are disappointed in this outcome, the study provided a clear answer," said Martina Flammer, M.D., Chief Medical Officer of Insmed, in a statement. The news casts a shadow on the drug's potential to become a blockbuster therapy for a wide range of inflammatory conditions.
However, the negative result is starkly contrasted by brensocatib's recent major success in its primary indication. The same drug, which will be marketed as Brinsupri, recently secured FDA approval for treating bronchiectasis, a chronic lung disease. That approval was based on the successful Phase 3 ASPEN study, which showed the drug significantly reduced the frequency of pulmonary exacerbations, a key goal for patients.
This context is critical for investors in the roughly $42 billion company. While the failure in CRSsNP halts one avenue of expansion, the core commercial opportunity for Insmed remains the launch of Brinsupri for bronchiectasis, which analysts widely expect to be a major growth driver.
In a separate move signaling a strategic diversification, Insmed also announced it has acquired the rights for the development and commercialization of tislelizumab in Greater China from BeiGene. Tislelizumab is an anti-PD-1 monoclonal antibody, a well-established class of cancer immunotherapy drugs. The deal marks Insmed's entry into the competitive but lucrative oncology market, a move likely intended to build out a pipeline independent of brensocatib.
Despite the trial failure, Wall Street has largely maintained a positive outlook on Insmed, with a strong majority of analysts rating the stock as a 'Buy'. This consensus is built on the commercial prospects of Brinsupri in bronchiectasis and the potential of other assets in the company's pipeline, including treatments for pulmonary arterial hypertension (PAH) and hidradenitis suppurativa (HS).
The day's events present a mixed narrative for Insmed. The BIrCh trial's failure is an undeniable pipeline setback that narrows the peak sales potential for brensocatib. Yet, with a major drug approval already secured and a strategic entry into oncology, the company's long-term trajectory will now hinge on a successful commercial launch of Brinsupri and continued progress in its remaining clinical programs.