Background:

PC-766B is a macrolide antibiotic existed in anactinomycete strain SC-4710.

PC-766B was active against Gram-positive bacteria, and some fungi and yeasts, yet inactive against Gram-negative bacteria. PC-766B exhibited potent cytotoxicity against murine tumor cell lines in vitro. The IC50 values against P388 leukemia and B16 melanoma were 0.1 and 0.5 ng/ml, respectively [1]. Intraperitoneal administration of PC-766B (0.25mg/kg/day) showed in vivo antitumor activity against P388 leukemia. PC-766B showed a weak inhibitory activity against Na+, K+-ATPase [1].

Reference:
[1] KUMAGAI K, TAYA K, FUKUI A, et al.  PC-766B, A NEW MACROLIDE ANTIBIOTIC PRODUCED BY Nocardia brasiliensis[J]. The Journal of antibiotics, 1993, 46(6): 972-978.