MBL-61, or MOB-61, also known as 1-methyl-2-bromo-LSD, is a serotonin receptor modulator of the lysergamide family related to lysergic acid diethylamide (LSD). It is the 1-methyl derivative of 2-bromo-LSD (BOL-148). Extensive metabolism of other 1-methylated lysergamides to their secondary amine derivatives, for instance methysergide (1-methylmethylergometrine) conversion into methylergometrine, has been observed. Similarly to the case of 2-bromo-LSD, MBL-61 was inactive as a psychedelic in humans at doses of up to 10 to 14mg orally. However, whereas 2-bromo-LSD can reportedly still produce some hallucinogenic effects at high doses, such effects are said to be completely lost in the case of MBL-61. In any case, both drugs are still potent serotonin receptor modulators like LSD, with MBL-61 having 5.3-fold the antiserotonergic activity of LSD in vitro and the highest degree of antiserotonergic activity of any other assessed lysergamide. MBL-61 was first described in the scientific literature by Albert Hofmann and colleagues in 1957.