α-Methyltryptophan (αMTP or α-MTP) is a synthetic tryptamine derivative, an artificial amino acid, and a prodrug of α-methylserotonin (αMS).

[1][3] αMTP has been suggested for potential therapeutic use in the treatment of conditions thought by some authors to be related to serotonin deficiency, such as depression.

[1] In labeled forms, αMTP is also used as a radiotracer in positron emission tomography (PET) imaging to assess serotonin synthesis and certain other processes.

[3][4][5] The preceding limitations of tryptophan make its use in PET imaging in humans impossible, whereas αMTP is a viable agent for such purposes.

[5] αMTP is first converted by tryptophan hydroxylase into α-methyl-5-hydroxytryptophan (αM-5-HTP or α-methyl-5-HTP), the α-methylated analogue of 5-hydroxytryptophan (5-HTP), prior to being decarboxylated by aromatic L-amino acid decarboxylase (AAAD) into αMS.