Seattle Genetics to present SGN-75 phase I data at ESMO Congress

August 18, 2017

Results of the '181' trial showed that the addition of Vectibix to FOLFIRI (an irinotecan-based chemotherapy) significantly improved PFS (co-primary endpoint) (median 5.9 months for Vectibix plus FOLFIRI versus 3.9 months for patients treated with FOLFIRI alone, hazard ratio 0.73; 95 percent CI: 0.59-0.90;>KRAS mCRC. Although numerically greater (median 14.5 months versus 12.5 months; hazard ratio 0.85; 95 percent CI: 0.70-1.04), the improvement in overall survival (co-primary endpoint) in the Vectibix arm did not achieve statistical significance>The addition of Vectibix to chemotherapy in the '181' trial resulted in greater than a three-fold improvement (35 percent versus 10 percent) in response rate in the wild-type KRAS patient population, as measured by a blinded central review. Tumor KRAS status was ascertained in 91 percent of the 1,186 patients enrolled in the '181' trial, the highest number ever prospectively reported for a second-line trial. In this study, the addition of Vectibix had no positive or negative effect on PFS or OS in patients with tumors harboring activating KRAS mutations.

"The response rate seen in the '181' trial is among the highest ever reported in the second-line metastatic colorectal cancer setting," said Emily Chan, M.D., Ph.D., Assistant Professor of Medicine, Vanderbilt-Ingram Cancer Center and '181' study investigator and author. "Additionally, the tissue acquisition from both the '181' and '203' studies has yielded a large repository of informative data regarding the KRAS biomarker, and holds the potential of providing even more information in the future."

In general, adverse events rates were comparable across arms in both studies, with the exception of known toxicities associated with anti-EGFR therapy, such as rash, diarrhea, and hypomagnesemia. Vectibix-related grade 3/4 infusion reactions were reported in less than one percent of patients.

Originally designed to compare the treatment effect in the overall mCRC patient population, both studies were amended to analyze outcomes with respect to the presence or absence of activating mutations in KRAS in the tumor itself. These are the first Phase 3 studies to prospectively analyze the effect of an EGFR inhibitor based on KRAS status in patients with previously treated mCRC.

Results from both trials were previously presented at Europe's largest cancer conference, ECCO 15 ?? ESMO 34, in September 2009, at the 2010 American Society of Clinical Oncology (ASCO) Gastrointestinal Cancers Symposium in January, and at the 2010 American Society of Clinical Oncology (ASCO) Annual Meeting in June.