Results from a closely watched clinical trial of an Alnylam Pharmaceuticals rare disease drug are due within three weeks, the company said Thursday as it reported earnings for the second quarter.

The study, called APOLLO-B and testing Alnylam’s medicine Onpattro in patients with a genetic heart condition, is viewed as vital to the biotechnology company’s future and initial data have therefore been eagerly anticipated by investors.

But investors, doctors and patients will have to wait a little longer, as Alnylam still isn’t ready to share results. The company previously said it planned to share data in the middle of the year, raising expectations that a trial readout could be announced alongside earnings.

“We’re on the cusp of seeing results” from the trial, said Alnylam CEO Yvonne Greenstreet, speaking on a Thursday conference call.

Onpattro, Alnylam’s first medicine, is already approved in the U.S. to treat nerve damage that arises from a disease called transthyretin amyloidosis. But the condition can affect the heart, too, and that form is thought to be potentially more prevalent. APOLLO-B is the company’s attempt to prove Onpattro can effective treat the heart as well as nerve symtpoms of transthyretin amyloidosis.

Last June, Alnylam completed enrolling patients in the study, which is designed to follow participants for one year and assess their heart health via a walking test.

But the recent trial failure of another drug being studied for the disease has raised questions about that study assessment and the likelihood that Alnylam will be able to show a positive effect for treatment.

Should Alnylam succeed, analysts view Onpattro as likely to become a blockbuster medicine and aiding the biotech in its goal of reaching sustained profitability after decades of research and losses. On Thursday, Alnylam reported product revenue of $214 million against a net loss of $277 million for the second quarter.

Shares in Alnylam fell by 1.5% in Thursday morning trading, consistent with a drop in value for a broader biotech index.