Insmed’s Brinsupri stumbles again in second failed trial in four months

USA—Insmed, a New Jersey-based biotech company, has faced another major setback after its experimental drug Brinsupri failed to demonstrate effectiveness in treating hidradenitis suppurativa (HS), a painful inflammatory skin condition.

This marks the second significant trial failure for the medication in just four months, prompting the company to suspend development in this indication.

Trial results disappoint expectations

The phase 2b study, which included 214 patients with moderate to severe HS, showed that Brinsupri did not work any better than a placebo.

Patients receiving the 10 milligram dose showed a 46 percent reduction in abscesses and inflammatory nodules, while those on the 40 milligram dose experienced a 40 percent reduction.

By comparison, the placebo group achieved a 57 percent reduction, underscoring the drug’s inability to outperform the inactive treatment.

HS causes painful lumps, abscesses, and scarring in sweat gland areas, making it a debilitating condition for those affected.

Despite the medication’s failure in this population, the study did provide some encouraging data regarding safety.

Safety profile remains strong

Side effects occurred more frequently in the lower-dose group, with 55 percent of patients in the 10 milligram arm experiencing treatment-related adverse events compared to 46 percent in the placebo group and 43 percent in the 40 milligram group.

Three serious adverse events occurred in the lower-dose group, whereas the placebo and higher-dose groups each reported only one serious event.

Analysts at Mizuho Securities identified the trial’s strongest takeaway: the drug maintained an “excellent safety and tolerability profile,” suggesting that adverse effects remain manageable at these dose levels.

Previous failure compounds concerns

This setback comes after Brinsupri’s failed phase 2 trial for chronic rhinosinusitis without nasal polyps, which did not achieve its main goals at either of the tested doses.

That earlier failure in December prompted analysts to significantly downgrade revenue projections for the medication, reducing peak annual sales expectations from USD16 billion to USD11 billion.

Explanations and market impact

Insmed’s chief medical officer, Dr. Martina Flammer, attributed the HS trial challenges to a lack of established animal models for studying the condition, which complicates clinical development efforts.

Nevertheless, she expressed hope that findings from this study would advance scientific understanding of the disease.

William Blair analyst Matt Phipps noted that the disappointing result was “not surprising” given previous challenges in HS research, particularly high placebo response rates.

He indicated the failure would have “minimal impact” on Insmed’s stock valuation, citing already-low market expectations for this particular trial.

Commercial progress elsewhere

Brinsupri received approval in August 2024 for treating bronchiectasis, a chronic lung disease.

Since reaching pharmacies just over four months ago, the medication generated USD173 million in sales, with first-quarter 2025 estimates reaching USD198 million according to Visible Alpha consensus data.

Despite these recent setbacks in expansion efforts, the drug’s established indication continues driving revenue growth for the company.

On the day following the announcement, Insmed’s stock price edged upward by nearly one percent in pre-market trading, suggesting investors had largely anticipated unfavorable results.