Shares of Puma Biotechnology (PBYI) are sinking after Roche (RHHBY) reported that its Phase III breast cancer study met its primary endpoint.

The data showed that adjuvant treatment with the combination of Perjeta, Herceptin and chemotherapy achieved a statistically significant reduction in the risk of recurrence of invasive disease or death in people with HER2-positive early breast cancer compared to Herceptin and chemotherapy alone.

TheStreet’s Adam Feuerstein tweeted this morning, ” $RHHBY wins w/ APHINITY study, fatal blow to $PBYI neratinib.” Citi analyst Yigal Nochomovitz, on the other hand, said on February 1 that Puma shares could fall as much as 30% if Roche’s study succeeds. The analyst recommended buying Puma shares on the weakness on the belief that neratinib should still be approved by the FDA for extended adjuvant. In pre-market trading, Puma shares are down 12% to $33.60.