Carbidopa/oxitriptan

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Carbidopa / oxitriptan
Carbidopa.svg
5-Hydroxy-L-Tryptophan (5-HTP).svg
Carbidopa (top) and oxitriptan (bottom)
Combination of
Carbidopa Aromatic L-amino acid decarboxylase inhibitor
Oxitriptan Serotonin precursor
Clinical data
Other namesCarbidopa/5-hydroxytryptophan; Carbidopa/L-5-hydroxytryptophan; Carbidopa/5-HTP; Carbidopa/L-5-HTP; EVX-101; EVX101
Routes of
administration 		Oral [1] [2]

Carbidopa/oxitriptan (developmental code name EVX-101), or carbidopa/5-hydroxytryptophan (carbidopa/5-HTP), is a combination of 5-hydroxytryptophan (5-HTP; oxitriptan), a serotonin precursor, and carbidopa, a peripherally selective aromatic L-amino acid decarboxylase (AAAD) inhibitor, which is under development as an add-on therapy for the treatment of obsessive–compulsive disorder (OCD) in people taking a selective serotonin reuptake inhibitor (SSRI). [1] [3] [4] [2] It is or was also under development as an antidepressant for the treatment of depressive disorders in people taking an SSRI or serotonin–norepinephrine reuptake inhibitor (SNRI) with an inadequate treatment response, but no recent development has been reported for this indication. [1] [3] [5]

Contents

The drug is taken orally. [1] It is a gastro-retentive sustained-release formulation of 5-HTP (250 mg per tablet) and low-dose carbidopa (0.3125–2.5 mg per tablet). [2] Use of 5-HTP alone is impractical due to poor pharmacokinetics and rapid metabolism. [2] [6] Carbidopa enhances the pharmacokinetics of 5-HTP, for instance greatly increasing its oral bioavailability (with levels increased by ~14-fold). [2] [6] The elimination half-life of 5-HTP in combination with carbidopa was found to be 4.1 to 6.5 hours and was doubled compared to 5-HTP alone. [2] [6] The purpose of carbidopa/oxitriptan add-on therapy is to further increase serotonin levels beyond that provided by an SSRI alone. [2] Circulating cortisol levels increased with the drug, which is a known biomarker for brain serotonin elevation. [2] Carbidopa/oxitriptan is analogous to carbidopa/levodopa, which contains carbidopa and the dopamine precursor levodopa (L-DOPA) and is approved and used to elevate brain dopamine levels to treat Parkinson's disease. [7]

Carbidopa/oxitriptan is under development by Evecxia. [1] [3] As of October 2025, it is in phase 1 clinical trials for OCD, with a phase 2 trial being planned. [1] [3] [4] [8]

Besides for depression and OCD, the combination of 5-HTP with a peripherally selective AAAD inhibitor such as carbidopa or benserazide is being studied for the treatment levodopa-induced dyskinesia in people with Parkinson's disease. [6] [9] [10]

See also

References

  1. 1 2 3 4 5 6 "Carbidopa/oxytriptan - Evecxia". AdisInsight. Springer Nature Switzerland AG.
  2. 1 2 3 4 5 6 7 8 Carpenter D, McKenzie L, Beaudoin S, Totaro C, Zann V, Hart J, Klein R, Raskin J, Jacobsen J (June 2023). A Phase 1 SAD and MAD Trial of EVX-101, A Novel Gastro-Retentive Prolonged-Release 5-HTP/Low-Dose Carbidopa Tablet, in Healthy Subjects Taking Escitalopram (PDF). 2023 Annual Meeting of the American Society of Clinical Psychopharmacology (ASCP), Miami Beach, FL; May 30-June 2.
  3. 1 2 3 4 "Delving into the Latest Updates on EVX-101 with Synapse". Synapse. 8 May 2025. Retrieved 12 January 2026.
  4. 1 2 Chowdhry, Amit (23 September 2025). "Evecxia Therapeutics: $5 Million Secured To Advance OCD and Depression Treatments". Pulse 2.0. Retrieved 12 January 2026.
  5. ↑ "Evecxia Therapeutics Reports Favorable Data From a Phase 1 Single-Ascending Dose and Multiple-Ascending Dose Trial of Adjunctive EVX-101 in Healthy Volunteers Treated With a First-Line Antidepressant". BioSpace. 10 April 2023. Retrieved 12 January 2026.
  6. 1 2 3 4 Meloni M, Puligheddu M, Sanna F, Cannas A, Farris R, Tronci E, Figorilli M, Defazio G, Carta M (August 2020). "Efficacy and safety of 5-Hydroxytryptophan on levodopa-induced motor complications in Parkinson's disease: A preliminary finding". J Neurol Sci. 415 116869. doi:10.1016/j.jns.2020.116869. hdl: 11584/289233 . PMID   32464351. The half-life of 5-HTP in healthy subjects is relatively short (4.3±2.8 hr) [27], and, unless dosed very frequently, entails highly fluctuating exposure, limiting the 5-HTP's therapeutic potential [28]. In a recent study of healthy volunteers, the addition of carbidopa resulted in a 14-fold increase in 5-HTP plasma levels. Specifically, 5-HTP 100 mg with coadministration of carbidopa resulted in a doubling of the elimination half-life, with an apparent clearance at least 14 times smaller, and a 15.4 times greater area under the curve compared to the same 5-HTP dosage without carbidopa [28].
  7. ↑ Müller T (May 2020). "Pharmacokinetics and pharmacodynamics of levodopa/carbidopa cotherapies for Parkinson's disease". Expert Opin Drug Metab Toxicol. 16 (5): 403–414. doi:10.1080/17425255.2020.1750596. PMID   32238065.
  8. ↑ "Evecxia Provides Financing & Corporate Updates Including Plans for an EVX-101 Proof-of-Concept Phase 2 Clinical Study in Obsessive-Compulsive Disorder (OCD) Responding Inadequately to First-line Therapies". BioSpace. 23 September 2025. Retrieved 12 January 2026.
  9. ↑ Meloni M, Figorilli M, Carta M, Tamburrino L, Cannas A, Sanna F, Defazio G, Puligheddu M (September 2022). "Preliminary finding of a randomized, double-blind, placebo-controlled, crossover study to evaluate the safety and efficacy of 5-hydroxytryptophan on REM sleep behavior disorder in Parkinson's disease". Sleep Breath. 26 (3): 1023–1031. doi:10.1007/s11325-021-02417-w. PMC   9418091 . PMID   34403081.
  10. ↑ Choi Y, Huh E, Lee S, Kim JH, Park MG, Seo SY, Kim SY, Oh MS (July 2023). "5-Hydroxytryptophan Reduces Levodopa-Induced Dyskinesia via Regulating AKT/mTOR/S6K and CREB/ΔFosB Signals in a Mouse Model of Parkinson's Disease". Biomol Ther (Seoul). 31 (4): 402–410. doi:10.4062/biomolther.2022.141. PMC   10315339 . PMID   36918741.
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