Amgen's Denosumab Delay Not a Deal-Breaker; Cancer Remains the Big Question

The FDA's complete response letter to Amgen regarding approval of denosumab in two of six pending indications was an unpleasant surprise that could have been much worse, but the drug's biggest test is yet to come.

As BNET previously reported, denosumab (a.k.a. Prolia) is expected to be the knight in shining armor that will save Amgen from declining flagship product sales.

Amgen was angling for approval in both the treatment and prevention of three kinds of bone loss: that associated with menopause, with prostate cancer hormone therapy, and with breast cancer hormone therapy. Two months ago, an FDA advisory committee gave the drug a thumbs up in the postmenopausal and prostate treatment indications and a thumbs down everywhere else.

An FDA decision on the prostate and breast bids is yet to come, but Amgen revealed this morning that the agency issued a complete response letter for postmenopausal prevention and treatment. In the former, a time-consuming new clinical trial is needed, but in the latter, the FDA asked for post-marketing surveillance info that analysts expect will be resolved in relatively short-order.

Still, the setback clearly caught Amgen by surprise: In Vivo Blog notes that the company had already launched a Prolia reimbursement page on its website, which it subsequently yanked down. And as CNBC pointed out, "World Osteoporosis Day" on Tuesday might be a bit less of a party without Amgen (although considering that competitors Eli Lilly and Novartis are among the celebration's sponsors, maybe Amgen's delay will make them all the merrier.)

Regardless, Deutsche Bank analyst Mark Schoenebaum notes that postmenopausal osteoporosis treatment, at more than $1 billion annually, is by far the biggest indication of denosumab's first six approval bids. He values the other five indications at maybe $325 million combined, so Amgen (almost, once a few i's are dotted and t's are crossed) won where it counts.

But denosumab also is being studied for the reduction of fracture risk in various cancers, as well as for the prevention of bone metastases. Those applications have yet to go to the FDA, but Schoenebaum predicts the combined markets could be worth upwards of $3 billion annually, making them even more critical to denosumab's success and Amgen's future.