Late treatment of murine lupus erythematosus with dactinomycin (actinomycin D). I. Course and longevity.

Dactinomycin treatment a of group of (NZB X NZW)F1 hybrid female mice was delayed until the age of 6-6 1/2 months, by which time the immune complex disease was well established. Three animals of the original twenty-eight had already died, ten had heavy proteinuria and a few were oedematous. The dactinomycin dose was 3.5 microgram per day, which was suspended when significant weight loss occurred. Twelve of the thirteen experimental mice were alive at 12 months of age, eleven at 15 months, but only eight by 20 months, whereas all twelve control animals had died by the age of 11 months. These results and the supporting data on body weight and renal function indicate that dactinomycin can at least arrest the disease process and may improve it. The mechanism is not known, but it may be the result of a reduced availability of DNA or an alteration in its properties following combination with dactinomycin.