Phase II evaluation of N-(phosphonacetyl)-L-aspartic acid (PALA) in metastatic adenocarcinoma of the colon or rectum.

N-(Phosphonacetyl)-L-aspartic acid (PALA) was administered at a dose of 1.5 g/m2/day x 5 days in a phase II evaluation of 21 patients with metastatic adenocarcinoma of the colon or rectum. Courses were repeated every 3 weeks. No responses were seen, but 11 patients had disease stabilization. PALA toxicity was marked, causing discontinuation of therapy in two patients. Major toxicity was cutaneous (90%), mucosal (35%), and gastrointestinal (diarrhea, at times bloody) (50%). There was no evidence of myelosuppression or CNS toxicity. PALA appears inactive in patients with metastatic colorectal carcinoma in the dose and schedule used in this study.