Amgen Reports Results From Phase 3 PRIME 203 Trial For Vectibix

Published: 05-Nov-2009

The study fails to meet a secondary endpoint of overall survival

Amgen has reported that the Phase 3 PRIME 203 trial evaluating Vectibix (panitumumab) administered in combination with Folfox (an oxaliplatin-based chemotherapy) as a first-line treatment of metastatic colorectal cancer (mCRC) has failed to meet a secondary endpoint of overall survival.

The prospective analysis of the 203 study showed that Vectibix, when added to a Folfox chemotherapy regimen in patients with KRAS wild-type mCRC, resulted in a median overall survival of 23.9 months compared to 19.7 months for patients treated with Folfox alone. The median overall survival difference of 4.2 months in the Vectibix arm did not reach statistical significance.

In the study, overall survival appeared to be reduced in patients with KRAS mutant tumors receiving Vectibix. Although not statistically significant, this result emphasises the importance, as described in product labeling, of ensuring that patients receiving Vectibix do not bear tumors containing KRAS mutations.

Amgen said that originally designed to compare the treatment effect in the overall population, the study was amended to analyse outcomes with respect to the presence or absence of activating mutations in KRAS in the tumor itself. Tumor KRAS status was ascertained in more than 90% of the 1,183 patients enrolled in the trial.

The company presented available results from the trial at the 2009 ECCO 15 - ESMO 34 European Multidisciplinary Congress in Berlin, showing that Vectibix significantly improved median progression-free survival by 1.6 months (9.6 versus 8 months for patients treated with Folfox alone, in patients with KRAS wild-type mCRC (primary endpoint).

Moreover, Vectibix to chemotherapy also improved response rate in the KRAS wild-type patient population as measured by blinded central review (55% versus 48% in the Folfox only arm).

Roger Perlmutter, executive vice president of research and development at Amgen, said: "As we previously announced, the 203 study met its primary endpoint of progression-free survival in the first-line treatment of patients with KRAS wild-type metastatic colorectal cancer. While not statistically significant, we are also encouraged by the positive trend of the data for overall survival for these patients treated with Vectibix."

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