Why #ASCO18 Caused Blueprint Medicines Shares To Tumble Up to 16% Today

What happened

After clinical-stage competitor Loxo Oncology (NASDAQ: LOXO) presented impressive data at the American Society of Clinical Oncology (ASCO) meeting this weekend, shares in Blueprint Medicines (NASDAQ: BPMC) tumbled by as much as 16% on Monday.

So what

In April, Blueprint Medicines reported solid efficacy from an early-stage study of BLU-667, a precision medicine targeting cancer in patients with RET ("rearranged during transfection") fusions.

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In BLU-667's study, the preliminary overall response rates (ORR) were 50% in 14 patients with non-small cell lung cancer (NSCLC) and 40% in 25 patients with medullary thyroid cancer (MTC).

However, Loxo Oncology is also working on a RET-fusion drug, Loxo-292, and over the weekend, data was unveiled on it that investors are interpreting as better than Blueprint Medicines' BLU-667. Specifically, as of the data cutoff for the presentation, 77% of NSCLC patients and 45% of MTC patients responded to Loxo-292.

Separately, another competitor, Deciphera Pharmaceuticals (NASDAQ: DCPH) reported a 24% ORR and 80% three-month disease control rate in combined second-line and third-line patients with gastrointestinal stromal tumors (GIST). Like Blueprint Medicines' avapritinib, Deciphera's drug, DCC-2618, targets mutations to kinase enzymes (KIT and PDDGa) that can contribute to cancer proliferation and survival.

Now what

Although you can't compare efficacy in separate trials, that's exactly what's happening today. Perhaps the biggest takeaway is that targeting RET fusions and KIT/PDDGa mutations is a successful strategy that may pay off for all of these clinical-stage companies.

The data from all these competing trials is from early-stage studies involving a relatively small number of people, so the data could change markedly for all of these companies as time passes and more people are enrolled.

Personally, I think precision medicines like those being developed by these companies represent the next big thing in how we treat cancer, so I'm inclined to buy Blueprint Medicine's shares on this drop, not sell them. This is especially true given that Blueprint Medicine plans to update industry watchers on data from its avapritinib GIST trial at the 23rd Congress of the European Hematology Association (EHA) on June 15.

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Todd Campbell has no position in any of the stocks mentioned. His clients may have positions in the companies mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.