A Phase I study of escalating doses of the tyrosine kinase inhibitor semaxanib (SU5416) in combination with irinotecan in patients with advanced colorectal carcinoma.

BACKGROUND

One of the most studied pro-angiogenic factors involved in the development of colorectal cancer is the vascular endothelial growth factor (VEGF). The small molecule tyrosine kinase inhibitor semaxanib (SU5416) is one of the several agents targeting the VEGF signaling pathway, and its development centered mostly in the treatment of colorectal cancer.

METHODS

We designed and conducted an NCI-sponsored trial to determine the maximum tolerated dose (MTD) and dose-limiting toxicities (DLTs) of semaxanib given twice weekly in combination with weekly irinotecan in patients with advanced colorectal cancer who had failed at least one prior treatment. The irinotecan dose was fixed at 125 mg/m(2) given weekly for 4 weeks followed by 2 weeks of rest. Patients with prior pelvic irradiation received a reduced dose of 100 mg/m(2). The semaxanib dose was escalated, going from 85 to 110 mg/m(2) and finally to 145 mg/m(2).

RESULTS

Ten patients were treated in our study and all were evaluable for toxicity. There were no drug-related Grade 4 toxicities. There was one episode of Grade 3 headache and one episode of Grade 3 vomiting. The most common Grades 1 and 2 toxicities included diarrhea, abdominal cramping, anemia and nausea. Nine patients completed at least one 6 week cycle of treatment and were considered evaluable for response. Among those nine, two had a partial response, three had stable disease and four had progressive disease after the first cycle.

CONCLUSIONS

Both irinotecan and semaxanib could be given at their full single-agent recommended doses without significant toxicity, and the combination showed signs of clinical activity. However, owing to discouraging results from Phase III trials, it is unlikely that this combination will be further explored.