SPIRITT - Second-Line Panitumumab Irinotecan Treatment Trial

This phase 2, multicenter, open-label, randomized, two-arm study was designed to estimate the treatment effect of panitumumab in combination with FOLFIRI compared to bevacizumab in combination with FOLFIRI in subjects with metastatic colorectal cancer (mCRC) who had failed first-line therapy with at least 4 doses of oxaliplatin-based chemotherapy and bevacizumab. After data became available demonstrating that the treatment effect of antiepidermal growth factor receptor (EGFR) agents was limited to patients with wild-type Kirsten rat Sarcoma-2 virus (KRAS) mCRC, the study was amended to enroll only subjects with wild-type KRAS tumors. Eligible subjects were randomized in a 1:1 ratio to receive panitumumab 6 mg/kg plus FOLFIRI once every 2 weeks (Q2W) or bevacizumab 5 mg/kg or 10 mg/kg plus FOLFIRI Q2W. Randomization was stratified by the reason for first-line treatment failure (progression vs toxicity) and by intended bevacizumab dose (5 mg/kg vs 10 mg/kg). The intended bevacizumab doses were ascertained from sites at the time of site initiation. Subjects were treated with all or any components of second-line treatment until the occurrence of unacceptable adverse events, disease progression, death, loss to follow up, or study withdrawal by the subject, investigator, or sponsor. Tumor response was evaluated by blinded central radiology review per modified Response Evaluation Criteria in Solid Tumors (RECIST) version 1.0 and by the investigator using either modified RECIST version 1.0 or clinical assessment. After subjects permanently discontinued all components of second-line treatment, they were to undergo a safety follow-up assessment 30 (± 7) days after the last dose. Subjects ending second-line treatment before disease progression were followed for PFS (radiographic disease assessment) every 12 weeks (± 14 days) from the safety follow-up visit until disease progression, initiation of a new therapy for mCRC, or until approximately 100 PFS events were observed in subjects with wild-type KRAS tumors. Subjects were also followed for survival every 12 weeks (± 14 days) from the safety follow-up assessment until approximately 100 PFS events were observed in subjects with wild-type KRAS tumors.