Array Biopharma Inc (NASDAQ:ARRY) just reported detailed topline from a recently completed oncology pivotal, and alongside the report, announced it expects to submit a New Drug Application (NDA) to the FDA before the end of this month. An announcement concerning the trial hit markets earlier in June, and Array gained on the suggestion that the candidate in question – Binimetinib – had hit its primary endpoint in the phase III. On the latest release, however, the company has declined circa 6%, as the detailed analysis tempered enthusiasm a little.

With this in mind, and as the agency filing data draws closer, what caused the (slight) sentiment shift, and what can we expect from the company going forward? Let’s take a look.

First, a look at the drug in question. As mentioned, it’s called Binimetinib, and its target indication – in the just completed trial – is a type of skin cancer called NRAS-Mutant Melanoma. Traditional (for want of a better word) melanoma has a very high survival rate, at least when compared to other cancer types. NRAS-Mutant Melanoma, however, is associated wit ha poor prognosis, and has a very high mortality rate. It affects circa 15-20% of individuals that get melanoma, and currently has very limited treatment options. There are some experimental immunotherapy treatments in circulation, but few that have any real level of efficacy comparable to the treatment of traditional skin cancer.

Binimetinib is what’s called an MEK inhibitor. MEK is a protein kinase that facilitates the function of what’s called the MAPK signaling pathway, which is a route through which signals pass to the nuclei of cells (in this case, cancerous cells) and initiate processes like proliferation, growth, etc. By inhibiting the function of MEK, Binimetinib (or so Array hopes) stops the MAPK pathway from telling cancerous cells to replicate. In doing so, it (again, as Array hopes) stops metastasis.

So that’s the theory, how closely have the data lined up with the hypothesis? To put it simple – very closely. The primary endpoint of the trial was progression free survival (PFS), and patients received either Array’s experimental drug or Dacarbazine, which is a currently available SOC for a host of cancers, including malignant melanoma. Patients that received Binimetinib recorded progression free survival of 2.8 months, while the SOC treatment are recorded PFS of 1.5 months. In an arm that saw patients receive the experimental drug after already having received an immunotherapy treatment, PFS (median) rose to 5.5 months versus 1.6 months for a control arm that received Dacarbazine.

Pretty good, right?

Well, yes, but then why has Array’s market capitalization taken a 6% hit on the detailed data? The only identifiable reason for the decline is the tolerability statistics. Grade 3/4 adverse events reported in greater than or equal to 5 percent of patients receiving binimetinib included increased creatine phosphokinase (CPK) and hypertension. These are two pretty serious AEs, and might play into the agency’s decision come PDUFA. That is, more likely from a labelling standpoint than an approval/decline standpoint.

The bottom line here is that this type of melanoma is very serious, has a high mortality rate and has very few currently available treatment options. The detailed analysis of the study may have offered up some less than desirable adverse events, and a pretty high rate of these AEs to boot, but when it comes to late stage oncology, serious AEs are to be expected.

If the FDA decides to add a warning to the drug on approval (that is, of course, assuming the agency does approve the drug based on the pivotal drawn efficacy data) then this may impact Array’s potential market. Having said this, it’s affair sized market – circa 20% of the 76,000 new cases in the US each year – and so long as the label doesn’t write off any more than, say, 25% at the top end of the patient population, there’s plenty of revenues to be generated from an approval and subsequent successful commercialization.

A discount opportunity based on the current pullback? Perhaps. There’s risk, as there always is with development stage biotech, but this one’s about as close as they come to a shoe in for approval based on pivotal. One to watch, and a potentially rewarding small scale allocation as part of a wider biotechnology portfolio.