Abstract
It was found that steroid-mediated nicotinamide -adenine dinucleotide (phosphate) transhydrogenases can be inhibited in vitro by folic acid and its antimetabolites. The most potent inhibitor was Methotrexate, a drug with a high therapeutic index against experimental cancer. The inhibitions produced by a combination of folic acid and the analogues were additive, as were those between the folic acid compounds and antagonistic steroid hormones.