Inotek Pharmaceuticals acknowledged today that its lead clinical candidate, the glaucoma treatment trabodenoson, failed a Phase III trial according to topline results, touching off a selloff that shrunk the company’s share price by nearly two-thirds this morning.

Trabodenoson missed its primary endpoint of superiority to placebo in reduction of intraocular pressure (IOP) at all 12 time points in the MATrX-1 trial, designed to assess the candidate in primary open-angle glaucoma (POAG) or ocular hypertension (OHT).

IOP was measured at four time points across three dosages of trabodenoson—3%/1000 μg once daily, 4.5%/1500 μg twice daily, and 6%/2000 μg once daily—on days 14, 28, 42, and 84 of MATrX-1. The trial assessed the efficacy, safety, and tolerability of trabodenoson over 3 months in 303 patients with a placebo arm as well as a timolol 0.5% arm.

Inotek attributed the failure in part to a placebo response that was 2 to 3 mmHg greater than that observed in Phase II.

“We are disappointed that the primary endpoint of superiority at all 12 time points was not achieved. This result was driven primarily by the unexpectedly stronger placebo response at the 8 a.m. time point,” Inotek president and CEO David P. Southwell said in a statement.

Southwell added that trabodenoson achieved several clinically meaningful secondary endpoints: The 6% dose was statistically superior to placebo at days 84, 42, and 14 and marginally superior at day 28. The daily IOP reduction from diurnal baseline at 3 months for this dose was 4.25 mmHg compared to 2.38 mmHg for placebo, and 5.29 mmHg for the timolol 0.5% twice-daily control arm.

Inotek also cited an analysis of patients with IOP reduction of 5 mmHg or greater from baseline, which it said indicated a statistically higher proportion of responders in the 6% trabodenoson group than the placebo group at all visits.

MATrX-1 topline results also suggested that trabodenoson is an active molecule with a unique safety profile, Inotek said, based on the candidate’s safety, tolerability, and low discontinuation rate.

“Later this quarter, we expect to receive additional data beyond the topline results reported today. Once we have the additional data, we will determine next steps in the trabodenoson monotherapy program,” Southwell added.

Trabodenoson is a first-in-class, highly selective adenosine mimetic targeting the A1 subreceptor. Trabodenoson is designed to lower IOP by augmenting the eye’s natural function of the trabecular meshwork.

Investors responded to Inotek’s trial failure news by sending shares of the company’s stock down 64% from its Friday closing price of $6.10, to $2.20 in premarket trading as of 9:10 a.m.

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