8-aminoquinolines effective against Pneumocystis carinii in vitro and in vivo.

The activities of 25 8-aminoquinolines were compared in tests assessing the ability of the compounds to inhibit the growth of Pneumocystis carinii in culture. Six compounds were effective at or below 0.03 microM: CDRI 80/53, NSC19894, NSC305805, NSC305812, WR182234, and primaquine. Four others were effective at between 0.2 and 0.03 microM: NSC305835, WR225448, WR238605, and WR242511. Fourteen drugs were also tested in a standard model of P. carinii pneumonia in rats at daily doses of 2 mg/kg of body weight in drinking water. CDRI 80/53, NSC305805, NSC305835, and WR225448 were extremely effective in the animal model. The effectiveness of WR238605, WR242511, and primaquine in the rat model has been reported elsewhere (M. S. Bartlett, S. F. Queener, R. R. Tidwell, W. K. Milhouse, J. D. Berman, W. Y. Ellis, and J. W. Smith, Antimicrob. Agents Chemother. 35:277-282, 1991). The length of the alkyl chain separating the nitrogens in the substituent at position 8 of the quinoline ring was a strong determinant of anti-P. carinii activity.