an anthracycline , serirubicin , of the formula : ## str1 ## wherein r represents the substituent : ## str2 ## is produced by a process which comprises cultivating a strain of streptomyces in a suitable culture medium under aerobic conditions , said strain having the ability to produce the anthracycline compound , serirubicin , and then recovering the anthracycline compound , serirubicin , from the cultured medium . this serirubicin , or an acid addition salt of the serirubicin , can be contained as the active ingredient in anti - tumor agents and in pharmaceutical compositions for treatment of infections induced by gram - positive microorganisms , whereby good results are attainable .