Dive Brief:

• Strong initial demand for Amgen and Novartis' new preventive migraine therapy Aimovig has reinforced expectations of blockbuster sales — for one analyst at least.
• Since Aimovig's approval in May, total weekly prescriptions for the anti-CGRP drug have climbed to nearly 10,000, with more than 3,000 patients beginning treatment by the 10th week of sales, according to data from Iqvia cited by Leerink.
• Based on that uptake, the investment firm has raised its forecasts for global sales of CGRP-targeting antibodies to nearly $4.5 billion by 2022. Analyst Geoffrey Porges predicts that Amgen and Novartis will capitalize on Aimovig's position as first to market and maintain a leading share despite anticipated approvals for rival drugs.

Dive Insight:

Anti-CGRP antibodies are the latest class of biologic drugs pegged by analysts for multi-billion dollar sales.

The first drug approved for migraine prevention since Allergan's Botox (onabotulinumtoxinA), Aimovig (erenumab) offers a new option for the 10 million Americans that Amgen estimates suffer from the debilitating headache condition. Inbound drugs that also target the CGRP​ protein — from Eli Lilly, Teva Pharmaceutical Industries and Alder Biopharmaceuticals — could also gain U.S. approvals and transform what's been an underserved market into one crowded with new treatments.

While that potential has underpinned rosy sales forecasts, other blockbusters-to-be in recent years have fizzled or run into resistance from payers. The PCSK9 inhibitors Praluent (alirocumab) and Repatha (evolucumab), as well as Novartis' heart medicine Entresto (sacubitril/valsartan) are noteworthy examples.

Perhaps seeking to avoid a similar fate, Amgen and Novartis priced Aimovig at a lower-than-expected $6,900 per year in an effort to win broad coverage for the drug.

So far, it seems that approach is paying off.

"The response to Aimovig in the marketplace is beyond our expectations," said Anthony Hooper, Amgen's head of global commercial operations, on a second quarter earnings call last month.

Amgen says negotiations with payers are progressing well, and that it has secured coverage for 30% of commercially insured lives in the U.S. Importantly, payers don't appear to be seeking extensive documentation for coverage, seeking only physician attestation that a patient has failed on existing generic therapies.

Early prescription data for Aimovig look encouraging, with Leerink's Porges calling the volume of new patient starts "very impressive" in an Aug. 20 note to investors.

Porges believes Amgen and Novartis are still working through pent-up demand for a new migraine option and estimates that as many as 75,000 patients will be taking Aimovig by the end of this year.

​​For those investors expecting an immediate boost to revenues, however, Porges indicated some patience might be needed.

"[R]eported revenues over the next 1 [to] 2 years will be undermined by significant discounting as Amgen, Lilly, and Teva all try to grab initial starts and long term patient share," the Leerink analyst wrote.

And most of the prescriptions being written are through Amgen and Novartis' drug trial program, which provides patients with Aimovig for free for the first two months.

"The majority of our business is in free drug, but we are rapidly converting that business to paid prescriptions," Hooper said.

Porges estimates sales of Aimovig to total only $40 million in 2018, but anticipates a significant jump to $480 million next year.

Amgen will need a strong market position, as Eli Lilly is expected to win approval for its galcanezumab this fall and Teva remains confident its own fremanezumab can launch this year as well.