Source: Amgen

Amgen's (NASDAQ:AMGN) Kyprolis has passed multiple clinical trials, but the failure today will overshadow the rest.

That's because the only thing that really matters to cancer patients is survival. Does the drug help the patient live longer?

Living longer without the disease progressing (progression free survival, or PFS) or responding to the drug (response rate) are helpful measures of a drug's potential, but in the end, survival is all that matters.

That goes double in Europe.

Kyprolis has been on the market in the U.S. for over two years based on phase 2 data showing 23% of multiple myeloma patients responded to Kyprolis after failing at least two prior treatments. Earlier this month, Amgen announced results from a trial dubbed ASPIRE, that showed Kyprolis in combination with Celgene's Revlimid and a corticosteroid helped patients live 8.7 months longer without their disease worsening (PFS) compared to Revlimid and the corticosteroid alone.

The latest study, dubbed FOCUS, measured the more important overall survival. Unfortunately Kyprolis was no better than the control arm where patients got low-dose dexamethasone or equivalent corticosteroids, plus optional cyclophosphamide.

Does that mean Kyprolis doesn't work?

Absolutely not.

The patients in FOCUS had failed a median of five treatments before entering the study. What FOCUS tells us is that Kyprolis isn't any better than the current standard of care for patients that have exhausted most of their other options.

The ASPIRE PFS data should be enough to change Kyprolis' accelerated approval into a full approval; Onyx Pharmaceuticals, the former owner of Kyprolis before Amgen bought the company, designed ASPIRE in conjunction with the FDA to do just that. The data even look good enough to justify changing the label so Kyprolis is approved for treating patients in combination with Revlimid that have failed as few as one prior treatment. Currently Kyprolis is approved for patients that have failed two prior treatments including a drug in the same class as Revlimid.

In Europe it's a different story

European regulators are likely to want to see overall survival. FOCUS was clearly designed with European regulators in mind. The name of the trial (CarFilzOmib for AdvanCed Refractory MUltiple Myeloma European Study) even contains "European" in the name -- finding FOCUS as an acronym is a little harder.

ASPIRE, another trial with a wonky acronym (CArfilzomib, Lenalidomide, and DexamethaSone versus Lenalidomide and Dexamethasone for the treatment of PatIents with Relapsed Multiple MyEloma), might be enough to gain approval in Europe -- it sounds like Amgen is going to give it a try -- but without overall survival data, it's going to be a tough sell.

Even if ASPIRE is good enough to gain approval in Europe, where there are actually more multiple myeloma patients than in the U.S., the lack of overall survival data may make it hard to gain reimbursement by national health organizations in Europe. The UK's National Institute for Health and Care Excellence (NICE), for instance, takes efficacy and pricing into account when determining whether it'll pay for a drug. And with two brand-name treatments in the regimen -- Kyprolis and Revlimid -- the combination isn't going to be cheap.

We don't have the full ASPIRE data -- perhaps at the American Society of Hematology (ASH) meeting in December -- but Amgen hinted that the overall survival data "showed a trend in favor" of the combination containing Kyprolis but that the difference wasn't statistically significant. Since this was only an interim look, it's possible that, as more patients progress, the difference might become statistically significant, and then Amgen could reapply for regulatory and/or reimbursement approval if Kyprolis ends up getting turned down without the survival data.