Puma Biotechnology Inc. got a mixed reception from physicians Monday morning after the company shared additional data from its pivotal breast cancer drug trial at the American Society of Clinical Oncology’s annual meeting in Chicago.

The news sunk the Westwood firm’s shares, which fell 13 percent Monday to close at $169.97.

While further illuminating neratinib’s benefits, the presentation raised questions about the drug’s risks, specifically a tendency to give patients severe diarrhea, wrote RBC Capital Markets analyst Simos Simeonidis in a research note.

But the data also showed the drug maintained its benefit for patients over two years as study participants continued to avoid a disease relapse, Simeonidis noted, adding that key patient subgroups derived more benefit than the overall group. He interpreted the data positively and reiterated RBC’s buy rating for Puma.

Stifel Nicolaus & Co. Inc. analyst Tom Shrader suspected physicians and possibly the Food and Drug Administration would want to see more data. Shrader and Cowen and Co. both reiterated their hold ratings.

Puma will dive deeper into the data tonight at an investor event at a downtown Chicago hotel ballroom.

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