Mairanovsky was born to a Jewish family in Batumi in 1899. 
Mairanovsky was the head of several secret laboratories in the Bach Institute of Biochemistry in Moscow (1928–1935). As the head of Laboratory No. 1 (1938–1946), he initiated the secret poison program conducted by the NKVD.  He used political prisoners for experiments with poisons. His classified PhD thesis defended in 1940 was entitled "Biological activity of the products of interaction of mustard gas with [human] skin tissues".
Mairanovsky participated personally in political assassinations as a member of Pavel Sudoplatov's team in the 1940s, including assassination of Isaiah Oggins.
He was arrested as a part of the doctors' plot in 1951, in connection with the case of Viktor Abakumov, and spent 10 years in prison. After his release, he headed a biochemical laboratory in Makhachkala, Dagestan ASSR.