3′,5′-Dichloroamethopterin (DCM) and amethopterin (MTX) were compared with respect to their ability to prolong the lifespan of mice with advanced leukemia (L1210) on subcutaneous and oral administration. In agreement with previous studies, subcutaneous DCM was markedly more effective than subcutaneous MTX in increasing the survival time of the mice. On oral administration, the antileukemic activity of both drugs was reduced. The reduction in the effectiveness of DCM via the oral route was so extensive that oral DCM was no more effective than oral MTX in increasing the survival time of the mice.

Whereas subcutaneous DCM was able to produce complete regression of the local tumor without body weight loss, reduction of the local tumor during oral DCM treatment was seen only in conjunction with severe body weight loss.

The advantage of the subcutaneous route over the oral route for DCM or MTX did not appear to be influenced by the schedule of treatment employed.

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Presented in part before the American Association for Cancer Research, Inc., April, 1960.

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