In vitro activity and in vivo efficacy of a new series of 9-deoxo-12-deoxy-9,12-epoxyerythromycin A derivatives.

Analogs of 9-deoxo-12-deoxy-9,12-epoxyerythromycin A with an epimeric hydroxy, amino, or ketone substitution at the 11 position of the macrolide ring and an amino or epimeric hydroxy substitution at the 4" position of the cladinose sugar were synthesized in an attempt to produce acid-stable derivatives of erythromycin with improved bioavailability and activity against gram-negative bacteria. These modifications produced compounds with in vitro activities which were generally similar to that of erythromycin. In mice, however, selected analogs were more active than was erythromycin against staphylococci, streptococci, Haemophilus influenzae, and Legionella pneumophila. In mice, the 11-keto (A-63881), 11-epiamino (A-69334), 11-epiamino-4"-amino (A-71671), and 11-epiamino-4"-epiamino (A-73020) analogs achieved peak concentrations in serum and lung, serum half-lives, and/or areas under the serum curve which were greater than those of erythromycin. Improved pharmacokinetics, as compared with those of erythromycin, may explain the increased in vivo antibacterial activities of these compounds.