The objective of this program is the development of new or improved therapeutic approaches to more effective antifol therapy of human cancer. Syntheses of new analogs of methotrexate (MTX) are being studied or carried out with the aim of identifying compounds having greater effectiveness than MTX against a broader spectrum of tumors. The specific aims may be outlined as follows: First, to synthesize MTX analogs with (a) modifications in the C9-N10 bridge, (b) changes in the glutamate portion that might alter transport without adversely affecting binding to dihydrofolate reductase or that might enhance binding to the reductase, and (c) a reduced pyrazine ring and alkyl groups at N5 and N10. Secondly, the analogs are to be evaluated for, (a) their ability to inhibit dihydrofolate reductase from L1210 leukemia cells and other sources, (b) their transport characteristics in both normal mouse cells and in cancer cells, and (c) their effects on the growth of murine neoplasms selected because of differences in responsiveness to MTX with emphasis on activity against solid tumors. The biological studies are being conducted by Dr. Francis M. Sirotnak of Sloan-Kettering Institute for Cancer Research under a collaborative agreement.