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(R)-MDMA

Clinical data
Other names	(R)-Methylenedioxy-methamphetamine; (R)-MDMA; (R)-(–)-MDMA; R(–)-MDMA; (–)-MDMA; (R)-Midomafetamine; (R)-(–)-Midomafetamine; (–)-Midomafetamine; Armidomafetamine; levo-MDMA; l-MDMA; EMP-01; EMP01; MM-402; MM402
Routes of administration	Oral
Drug class	Serotonin–norepinephrine releasing agent; Serotonin 5-HT2A receptor agonist; Entactogen; Empathogen
Pharmacokinetic data
Metabolism	CYP2D6
Elimination half-life	11–14 hours
Identifiers
IUPAC name (2R)-1-(1,3-benzodioxol-5-yl)-N-methylpropan-2-amine
CAS Number	81262-70-6
PubChem CID	667458
ChemSpider	580842
UNII	3947754WXW
ChEMBL	ChEMBL382757
Chemical and physical data
Formula	C11H15NO2
Molar mass	193.246 g·mol
3D model (JSmol)	Interactive image
SMILES C(CC1=CC2=C(C=C1)OCO2)NC
InChI InChI=1S/C11H15NO2/c1-8(12-2)5-9-3-4-10-11(6-9)14-7-13-10/h3-4,6,8,12H,5,7H2,1-2H3/t8-/m1/s1 Key:SHXWCVYOXRDMCX-MRVPVSSYSA-N

(R)-3,4-Methylenedioxy-N-methylamphetamine ((R)-MDMA), also known as (R)-midomafetamine or as levo-MDMA, is the (R)- or levorotatory (l-) enantiomer of 3,4-methylenedioxy-N-methylamphetamine (MDMA; midomafetamine; "ecstasy"), a racemic mixture of (R)-MDMA and (S)-MDMA. Like MDMA, (R)-MDMA is an entactogen or empathogen. It is taken by mouth.

The drug is a serotonin–norepinephrine releasing agent (SNRA) and weak serotonin 5-HT_2A receptor agonist. It has substantially less or no significant dopamine-releasing activity compared to MDMA and (S)-MDMA. In preclinial studies, (R)-MDMA shows equivalent therapeutic-like effects to MDMA, such as increased prosocial behavior, but shows reduced psychostimulant-like effects, addictive potential, and serotonergic neurotoxicity. In clinical studies, (R)-MDMA produces similar effects to MDMA and (S)-MDMA, but is less potent and has a longer duration.

(R)-MDMA was first described in enantiopure form by 1978. Under the developmental code names EMP-01 and MM-402, it is under development for the treatment of post-traumatic stress disorder (PTSD), social phobia, and pervasive development disorders (PDDs) such as autism. It is thought that (R)-MDMA might have a better safety profile than MDMA itself whilst retaining its therapeutic benefits.

Pharmacology

Pharmacodynamics

Preclinical studies

MDMA is a well-balanced serotonin–norepinephrine–dopamine releasing agent (SNDRA). (R)-MDMA and (S)-MDMA are both SNDRAs similarly. However, (R)-MDMA is several-fold less potent than (S)-MDMA in vitro and is also less potent than (S)-MDMA in vivo in non-human primates. In addition, whereas MDMA and (S)-MDMA are well-balanced SNDRAs, (R)-MDMA is comparatively much less potent as a dopamine releasing agent (~11-fold less potent in releasing dopamine than serotonin), and could be thought of instead more as a serotonin–norepinephrine releasing agent (SNRA) than as an SNDRA. In non-human primates, (S)-MDMA demonstrated significant dopamine transporter (DAT) occupancy, whereas DAT occupancy with (R)-MDMA was undetectable. Similarly, MDMA and (S)-MDMA were found to increase dopamine levels in the striatum in rodents and non-human primates, whereas (R)-MDMA did not increase striatal dopamine levels. As such, (R)-MDMA may be less psychostimulant-like than MDMA or (S)-MDMA.

In addition to its actions as an SNDRA, MDMA has weak affinity for the serotonin 5-HT_2A, 5-HT_2B, and 5-HT_2C receptors, where it acts as an agonist. (R)-MDMA shows higher affinity for the serotonin 5-HT_2A receptor than (S)-MDMA or MDMA. In addition, (R)-MDMA is more potent as an agonist of the serotonin 5-HT_2A receptor, acting as a weak partial agonist of this receptor, whereas (S)-MDMA shows very little effect. Conversely however, (S)-MDMA is more potent as an agonist of the serotonin 5-HT_2C receptor. Based on these findings, it has been hypothesized that (R)-MDMA may be more psychedelic-like than (S)-MDMA. However, although (R)-MDMA partially substitutes for lysergic acid diethylamide (LSD) in animal drug discrimination tests, it did not produce the head-twitch response, a behavioral proxy of psychedelic effects, at any tested dose. In any case, findings in this area are conflicting.

MDMA is a well-known serotonergic neurotoxin and this has been demonstrated both in animals and in humans. There is evidence that the serotonergic neurotoxicity of MDMA may be driven primarily by (S)-MDMA rather than (R)-MDMA. (R)-MDMA shows substantially lower or potentially no neurotoxicity compared to (S)-MDMA in animal studies. This has been the case even when doses of (R)-MDMA were increased to account for its lower potency than (S)-MDMA. However, more research is needed to confirm this in other species, such as non-human primates. In contrast to (S)-MDMA, (R)-MDMA does not produce hyperthermia in rodents, and this may be involved in its reduced risk of neurotoxicity, as hyperthermia augments and is essential for the serotonergic neurotoxicity of MDMA. The reduced potency of (R)-MDMA as a dopamine releasing agent may also be involved in its reduced neurotoxic potential, as dopamine release is likewise essential for the neurotoxicity of MDMA. The hyperthermia of MDMA may in fact be mediated by dopamine release. As (R)-MDMA is less neurotoxic than (S)-MDMA and MDMA or even non-neurotoxic, it may allow for greater clinical viability and prolonged regimens of drug-assisted psychotherapy.

(R)-MDMA and (S)-MDMA have shown equivalent effects in terms of inducing prosocial behavior in monkeys. However, (S)-MDMA shows higher potency, whereas (R)-MDMA shows greater maximal effects. Conversely, (S)-MDMA does not increase prosocial behavior in mice, whereas both MDMA and (R)-MDMA do so. MDMA and (S)-MDMA increase locomotor activity, a measure of psychostimulant-like effect, in rodents, whereas (R)-MDMA does not do so. (R)-MDMA likewise showed fewer reinforcing effects than (S)-MDMA in non-human primates. These findings further add to (R)-MDMA showing reduced psychostimulant-like and addictive effects compared to MDMA and (S)-MDMA.

Clinical studies

The first modern clinical study of the comparative effects of MDMA, (R)-MDMA, and (S)-MDMA was published in August 2024. It compared 125 mg MDMA, 125 mg (S)-MDMA, 125 and 250 mg (R)-MDMA, and placebo. (R)-MDMA increased any drug effect, good drug effect, drug liking, stimulation, drug high, alteration of vision, and alteration of sense of time ratings similarly to MDMA and (S)-MDMA. However, (S)-MDMA 125 mg was more potent in increasing subjective effects, including stimulation, drug high, happy, and open, among others, than (R)-MDMA 125 or 250 mg or MDMA 125 mg. Ratings of bad drug effect and fear were minimal with MDMA, (R)-MDMA, and (S)-MDMA. In contrast to expectations, (R)-MDMA did not produce more psychedelic-like effects than (S)-MDMA. Besides subjective effects, (R)-MDMA increased heart rate, blood pressure, and body temperature similarly to MDMA and (S)-MDMA, though it was less potent in producing these effects. Body temperature was notably increased to the same extent with (R)-MDMA 250 mg as with MDMA 125 mg and (S)-MDMA 125 mg.

The differences in effects between (R)-MDMA and (S)-MDMA may reflect the higher potency of (S)-MDMA rather than actual qualitative differences between the effects of (S)-MDMA and (R)-MDMA. It was estimated that equivalent effects would be expected with (S)-MDMA 100 mg, MDMA 125 mg, and (R)-MDMA 300 mg. The findings of the study were overall regarded as not supporting the hypothesis that (R)-MDMA would produce equivalent therapeutic effects as (S)-MDMA or MDMA whilst reducing safety concerns. However, more clinical studies were called for to assess the revised estimated equivalent doses of MDMA, (R)-MDMA, and (S)-MDMA.

Pharmacokinetics

The elimination half-life of (S)-MDMA is 4.1 hours, whereas the half-life of (R)-MDMA is 12 to 14 hours. In the case of racemic MDMA administration, the half-life of (S)-MDMA is 5.1 hours and the half-life of (R)-MDMA is 11 hours. (R)-MDMA shows cytochrome P450 CYP2D6 inhibition and lower levels of the metabolite 4-hydroxy-3-methoxymethamphetamine (HMMA) than (S)-MDMA.

History

(R)-MDMA was first described in the scientific literature in enantiopure form by 1978. It was described in a paper authored by Alexander Shulgin, David E. Nichols, and other colleagues.

Clinical development

(R)-MDMA is under development separately by Empath Biosciences (EmpathBio) and MindMed. It is being developed by Empath Biosciences for the treatment of PTSD and social phobia and it is being developed by MindMed for the treatment of PDDs or autism. As of 2024, the drug is in phase 1 clinical trials for both PTSD, social phobia, and PDDs/autism.

See also

• List of investigational hallucinogens and entactogens
• List of investigational autism and pervasive developmental disorder drugs
• List of investigational social anxiety disorder drugs

References

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20. Dunlap LE (2022). Development of Non-Hallucinogenic Psychoplastogens (Thesis). University of California, Davis. Retrieved 18 November 2024. Finally, since R-MDMA is known to partially substitute for LSD in animal models we decided to test both compounds in the head twitch response assay (HTR) (FIG 3.3C).3 The HTR is a well-validated mouse model for predicting the hallucinogenic potential of test drugs. Serotonergic psychedelics will cause a rapid back and forth head movement in mice. The potency measured in the HTR assay has been shown to correlate very well with the human potencies of psychedelics.18 Neither R-MDMA or LED produced any head twitches at all doses tested, suggesting that neither has high hallucinogenic potential.
21. Halberstadt AL, Geyer MA (2018). "Effect of Hallucinogens on Unconditioned Behavior". Curr Top Behav Neurosci. Current Topics in Behavioral Neurosciences. 36: 159–199. doi:10.1007/7854_2016_466. ISBN 978-3-662-55878-2. PMC 5787039. PMID 28224459. have been assessed in head twitch studies. Racemic and S-(+)-MDA reportedly induce WDS in monkeys and rats, respectively (Schlemmer and Davis 1986; Hiramatsu et al. 1989). Although does not induce the HTR in mice, both of the stereoisomers of MDMA have been shown to elicit the response (Fantegrossi et al. 2004, 2005b). 5-HT depletion inhibits the response to S-(+)-MDMA but does not alter the response to R-(−)-MDMA, suggesting the isomers act through different mechanisms (Fantegrossi et al. 2005b). This suggestion is consistent with the fact that S-(+)- and R-(−)-MDMA exhibit qualitatively distinct pharmacological profiles, with the S-(+)isomer working primarily as a monoamine releaser (Johnson et al. 1986; Baumann et al. 2008; Murnane et al. 2010) and the R-(−)-enantiomer acting directly through 5-HT2A receptors (Lyon et al. 1986; Nash et al. 1994). In contrast to their effects in mice, Hiramatsu reported that S-(+)- and R-(−)-MDMA fail to produce WDS in rats (Hiramatsu et al. 1989). The discrepant findings with MDMA in mice and rats may reflect species differences in sensitivity to the HTR (see below for further discussion).
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23. ^ "Delving into the Latest Updates on MM-402 with Synapse". Synapse. 1 November 2024. Retrieved 2 November 2024.

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