What happened

Shares of Alnylam Pharmaceuticals (ALNY -2.09%) finished down 11.9% on Wednesday, following the biotech's third-quarter earnings release.

This is the first earnings report following the approval of Onpattro, Alnylam's drug to treat hereditary transthyretin-mediated amyloidosis. As many a biotech has discovered, once a company becomes a commercial-stage biotech, investors start having instant expectations for sales -- expectations that Alnylam apparently wasn't able to meet.

Doctor talking to a patient at a table

Image source: Getty Images.

So what

In the first seven weeks of the launch, Onpattro generated a paltry $0.5 million. While that certainly sounds like a really slow start, it can take up to a couple of months to get a patient through the insurance process, set up for infusions, and onto a drug, so investors really shouldn't have been expecting much on the revenue line.

Management noted that it had 125 U.S. patients submit start forms during the quarter, which is a better measurement of demand. However, the company also noted that about 60% of those were already identified and taking the drug under an early access plan, so there was a bit of a bolus of patients ready to take the drug.

The next wave of patients -- management thinks there are about 3,000 patients in the U.S. -- are going to be harder to find. Onpattro is approved in Europe, too, but the launch for most counties in the EU will go even slower as management needs to establish reimbursement with government-sponsored healthcare plans.

Now what

Alnylam had $1.27 billion in the bank at the end of the third quarter, so it has a healthy runway to establish a successful launch.

And besides, with multiple drugs in late-stage development, long-term investors should be focused on the company's pipeline rather than on Onpattro's launch anyway.