The data will be presented during a poster session at the 2015 American Society of Clinical Oncology (ASCO) Gastrointestinal Cancers Symposium taking place in San Francisco from January 15 to 17.
In an exploratory analysis from the PEAK study (abstract #660), treatment with Vectibix compared to bevacizumab (Avastin) resulted in a significantly higher proportion of patients with earlier tumor shrinkage at week eight (64 percent vs. 45 percent, respectively; 95 percent CI, p=0.0232), and among responding patients, a significantly longer duration of response (11.4 vs. 8.5 months, respectively; 95 percent CI, p=0.0142) and greater depth of response (65 percent vs. 46 percent, respectively; p=0.0007).
Overall response rates (ORR) appeared to be similar between Vectibix and bevacizumab. This is consistent with observed overall survival (OS) and progression-free survival (PFS) rates, and with data previously reported. The safety profile of Vectibix was consistent with previously reported studies.
"These analyses help deepen our understanding of how Vectibix works when added to a standard first-line chemotherapy for the treatment of wild-type RAS metastatic colorectal cancer," said Sean E. Harper, M.D., executive vice president of Research and Development at Amgen.
"Our Vectibix clinical trial program continues to yield new insights regarding biomarkers and drug sequencing."
While the primary analysis from PEAK showed similar ORR between the Vectibix- and bevacizumab-based regimens, this exploratory analysis demonstrates that Vectibix produces early, sustained anti-tumor activity, which may in part explain the OS and PFS benefits seen with Vectibix versus bevacizumab in this trial.
A separate analysis from the Phase 3 PRIME study (abstract #537), demonstrated that there were no significant differences in quality of life among patients treated with Vectibix plus FOLFOX versus FOLFOX alone despite the incidence of adverse events associated with each treatment regimen.
The quality of life analysis included a scale that assessed mobility, self-care, usual activities, pain/discomfort and anxiety/depression.
Colorectal cancer is the third most common cancer found in both men and women in the U.S. and is the second leading cause of cancer deaths.1,2 Approximately 1.2 million cases of colorectal cancer are expected to occur globally each year.
The PEAK (Panitumumab Efficacy in Combination with mFOLFOX6 Against bevacizumab plus mFOLFOX6 in mCRC subjects with wild-type KRAS tumors) (‘509) study is a global, multicenter, randomized, interventional Phase 2 trial designed to compare efficacy of first-line Vectibix (panitumumab) in combination with mFOLFOX6 versus bevacizumab in combination with mFOLFOX6 in 285 previously untreated patients with wild-type KRAS exon 2 metastatic colorectal cancer (mCRC).
Primary endpoints include progression-free survival (PFS), and secondary endpoints include overall survival (OS), percentage of patients with objective response (OR), duration of response (DoR), depth of response (DpR) and safety.
Patients were randomized in a 1:1 ratio to receive 6 mg/kg of intravenous panitumumab and mFOLFOX6, or 5 mg/kg of intravenous bevacizumab and mFOLFOX6 every 14 days.
In the exploratory analyses of tumor assessments, DpR was defined as the percentage of tumor shrinkage at nadir (point in time between chemotherapy cycles in which a patient experiences low blood counts) or progression. Early tumor shrinkage (ETS) was defined as the proportion of patients with >30 percent tumor shrinkage at week eight.
The PRIME (Panitumumab Randomized trial In combination with chemotherapy for Metastatic colorectal cancer to determine Efficacy) (‘203) study is a global, multicenter, randomized Phase 3 study designed to evaluate Vectibix (panitumumab) in combination with FOLFOX versus FOLFOX alone in 1,183 patients with wild-type KRAS exon 2 metastatic colorectal cancer (mCRC).
Primary endpoints include progression-free survival (PFS), and secondary endpoints include overall survival (OS), objective response rate (ORR), duration of response (DoR) and safety.
Patients were randomized in a 1:1 ratio to receive 6 mg/kg of panitumumab (day 1) and FOLFOX (day 1 and 2), or FOLFOX (day 1 and 2) alone of each 14-day cycle.
In this analysis, quality of life (QoL) was assessed every four weeks until disease progression, and once at a safety follow-up, using the EuroQoL 5-domain health state index and overall health rating (OHR; 0-100 visual analogue scale).
Vectibix is the first fully human anti-EGFR antibody approved by the U.S. Food and Drug Administration (FDA) for the treatment of metastatic colorectal cancer (mCRC).
Vectibix was approved in the U.S. in September 2006 as a monotherapy for the treatment of patients with EGFR-expressing mCRC after disease progression after prior treatment with fluoropyrimidine-, oxaliplatin-, and irinotecan-containing chemotherapy.
In May 2014, the FDA approved Vectibix for use in combination with FOLFOX, as first-line treatment in patients with wild-type KRAS (exon 2) mCRC. With this approval, Vectibix became the first- and- only biologic therapy indicated for use with FOLFOX, one of the most commonly used chemotherapy regimens, in the first-line treatment of mCRC for patients with wild-type KRAS mCRC.