Nemifitide
A five-amino-acid antidepressant injected under the skin, tested in small trials and never approved
Nemifitide is a synthetic peptide of five amino acids that its developer, Innapharma, tested as a fast-acting antidepressant given by daily injection under the skin. It is gone from the blood within an hour, yet small trials reported benefits lasting weeks. The largest randomised trial, 81 patients, favoured the higher dose over placebo. No approval followed, and no trial has been published since 2008.
Used in human trials: 30 mg or 45 mg, Once a day, Monday to Friday, Subcutaneous (Study: randomised trial in major depression, 81 patients) Details ↓
Recommended Dosing
Used in human trials
No manufacturer dose exists for this use: these are amounts given in published trials, not recommendations.
Work out syringe units → · New to syringes? · All dosing data ↓
What is it?
Nemifitide is a short synthetic peptide: five amino acids, two of them chemically altered (a fluorinated phenylalanine and a hydroxylated proline), ending in an amide. It was developed in the late 1990s by a small company, Innapharma, as an antidepressant, first under the code INN 00835 and briefly under the name netamiftide. Its developers described it as a relative of melanocyte-inhibiting factor, a tiny brain peptide that had been studied in depression decades earlier.
The idea that set it apart was speed. Standard antidepressants take weeks to work; the early nemifitide trials reported improvement within days of a five-day course of injections, lasting through four weeks of follow-up. That is striking for a drug with a half-life of 15 to 30 minutes, gone from the blood within an hour or two of each dose. The trials never explained the mismatch, and no receptor target is named in any paper read.
The pharmacology itself is clean. In five phase 1 studies in over 100 healthy volunteers, single and repeated doses from 18 to 320 mg peaked in the blood at about 10 minutes, rose in proportion to dose and did not build up with daily dosing. The only drug-related side effects were pain or redness where the injection went in, mostly at the highest doses. A small study found a needle-free jet injector gave the same exposure as a needle.
The efficacy evidence is thinner. The early phase 2 trials enrolled 52 to 55 patients each and gave a fixed small dose for five or ten days. Their main positive results came from splitting patients by blood level: those who reached a higher concentration did better than those who did not and than placebo. That kind of analysis can point to a real dose effect, but it is also easy to over-read, and the authors themselves noted a large placebo response and small numbers.
The best trial is the 2006 randomised study of 81 outpatients, which compared 30 mg and 45 mg a day, given on weekdays for two weeks, with placebo. The 45 mg dose was significantly better than placebo at the time of peak effect, one week after the injections stopped; the 30 mg dose appeared weaker. In an exploratory analysis, both doses separated from placebo only in the more severely depressed half of the patients. Tolerability was good, with side effects no more common than on placebo.
After that the record goes quiet. A 2008 open-label study in 25 people with treatment-resistant depression used much higher doses, 40 to 240 mg a day, and reported that 11 responded, with re-treatment courses about two months apart for those who relapsed; with no placebo group, it cannot show the drug caused the improvement. The company had expected phase 3 trials in 2003, but none was ever reported or registered on ClinicalTrials.gov, and nemifitide was never approved anywhere.
Mechanism of Action
How nemifitide might work is not established. The papers describe it as a melanocyte-inhibiting factor analogue and report effects in a rat depression model and on platelet serotonin uptake, without naming a receptor.
MIF analogue
The rat study describes nemifitide as a peptide analogue of melanocyte-inhibiting factor, a small brain peptide earlier studied in depression.
Antidepressant-like effect in rats
In rats bred to model depression it increased swimming in the forced swim test, at low and high doses but not middle ones, and acted after five days.
Platelet serotonin uptake
In a phase 2 trial the rate of serotonin uptake by platelets rose more on the drug than on placebo; the authors offered it as a marker of response.
Short exposure, long effect
Blood levels peak at about 10 minutes and fall with a 15 to 30 minute half-life, while trials reported benefits lasting weeks; the papers do not explain the gap.
Published Research
Studies whose titles or abstracts name nemifitide or its code INN 00835, read from their PubMed abstracts on October 29, 2026: the phase 1 pharmacokinetic studies, the placebo-controlled and open-label trials in depression, the rat study and the developer profile. Broad reviews of new antidepressant targets that list it in passing are left out.
Phase 1: fast in, fast out
Five phase 1 studies run over three years gave single and repeated subcutaneous doses of 18 to 320 mg to more than 100 healthy volunteers. Blood levels peaked at 10 minutes and the half-life was 15 to 30 minutes in most people; exposure rose roughly in proportion to dose, and five daily doses did not accumulate. No serious or significant systemic side effects occurred; the drug-related events were pain or redness at the injection site, mostly at 240 and 320 mg.
Needle or needle-free injection
Twelve healthy volunteers received one injection: 40 mg by ordinary needle, or 40 or 80 mg by a needle-free jet injector. Peak levels came at 10 minutes in everyone; the two 40 mg methods gave equivalent exposure (peaks of 226 and 245 ng/mL), and 80 mg roughly doubled it. The only side effects were mild injection-site reactions that cleared within a day.
Phase 2 and platelet serotonin uptake
In a phase 2 trial, people with unipolar depression received INN 00835 or placebo under the skin once a day for five days. Rating scales showed a significant response after the five days, and the rate at which platelets took up serotonin rose more on the drug than on placebo (19 and 16 patients sampled); the authors propose this uptake as a biochemical marker of treatment, while noting the small numbers.
Pilot trial in 52 patients
Fifty-two people with major depression received INN 00835 or placebo for five days and were followed for four weeks. Improvement tracked the blood level one hour after dosing: patients above about 5 ng/mL did significantly better than those below it and than placebo. The authors call it a small pilot with a large placebo response and too few blood samples for full pharmacokinetics.
Sorting responders by cluster analysis
A reanalysis of a placebo-controlled trial of INN 00835 split patients into subgroups by how their rating-scale scores changed. Within the drug-treated groups, the differences in response were attributed to blood drug levels, and platelet serotonin uptake separated the subgroups the same way. It is a statistical reanalysis, not a new trial.
Five or ten days at a fixed dose
Fifty-five outpatients with major depression received 18 mg a day (under the earlier name netamiftide) for ten days, for five days followed by placebo, or placebo for ten days. No significant side effects were seen. Patients whose peak blood level reached at least 45.7 ng/mL responded in 89% of cases against 40% below it; onset was reported within 48 hours and the effect lasted through four weeks of follow-up.
Re-treatment in an open extension
Twenty-seven people from a phase 2 trial entered an open-label extension in which they were treated again, with the investigators and patients still blind to the first assignment. Two thirds (18) responded to re-treatment, and the effect lasted about 3.3 months between courses. The authors suggested testing 18 to 72 mg a day in later trials.
Randomised trial of 30 and 45 mg
Eighty-one outpatients with major depression were randomised to 30 mg, 45 mg or placebo, injected on weekdays for two weeks and followed for four more. The 45 mg dose beat placebo on the main depression scale at the point of peak effect, a week after treatment ended; in an exploratory split, both doses separated from placebo only in the more severely depressed half. Side effects were no more common than on placebo and nobody dropped out because of them.
Open pilot in refractory depression
Twenty-five people with long-standing depression that had not responded to other treatment received 40 to 240 mg a day for 10 to 20 doses in an open, single-centre study. Eleven responded on the main scale, seven of them for the rest of the treatment phase; nine sustained responders were re-treated when they relapsed over up to two years, with about two months between courses. There was no placebo group.
Rats bred to model depression
In Flinders Sensitive Line rats, a strain bred for exaggerated immobility in the forced swim test, nemifitide increased swimming at low and high doses but not at intermediate ones. One dose worked after five days, faster than fluoxetine, and its effect lasted longer than desipramine's. The paper describes nemifitide as an analogue of melanocyte-inhibiting factor (MIF).
Developer profile, 2003
A short drug profile: nemifitide was being developed by Innapharma for depression, a first phase 2 trial in moderately to severely depressed people had finished by June 2001, and the company expected phase 3 trials to start later in 2003.
Dosing Data
Nemifitide was never approved, so there is no label. These are the amounts given in the human studies carded above, all by injection under the skin.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
What a Buyer Needs to Know
What is sold, how it is mixed, stored and taken, and what is known about its safety, quality and legal status. Each part names its source. Where we have none, it says unknown.
What is sold
Unknown: we hold no label and no published test that says what forms or vial sizes Nemifitide is sold in. A vial's own label is a seller's claim, not a source.
Mixing a vial: a worked example
An arithmetic example, not a recommendation: a 10 mg vial mixed with 3 mL of bacteriostatic water holds 3,333.3 mcg per mL, so 30 mg, the first amount in the “Study: randomised trial in major depression, 81 patients” row (30 mg or 45 mg) would be 900.0 units, more than a 1 mL U-100 syringe holds. Put your own vial's numbers into the reconstitution calculator.
Source: dose: Used in human trials, PMID 16259645 (Dosing Data below); vial and water: the calculator's default example, not a vial size we have a source for.
Storage before and after mixing
Unknown: no label or published stability study on file says how to store Nemifitide, before or after mixing. The mixing guide sets out the general rules, with their sources: keep a mixed vial in the fridge, and use it promptly, as the bacteriostatic water label says of any drug dissolved in it. The 28 days often quoted is the limit for an opened multiple-dose vial from a manufacturer, an outer limit set for sterility, not a time a mixed solution has been shown to keep. Nobody has published how long Nemifitide stays intact once mixed.
How it is taken
As it was given in human studies: Subcutaneous (Once a day, Monday to Friday; Study: randomised trial in major depression, 81 patients).
For injection technique, sites and needle disposal, see the mixing guide.
Source: Used in human trials: the route and frequency of each row in Dosing Data below.
What to expect, and when
How long it stays in the body: not established by a measurement cited on this entry.
How long the doses were given: Study: randomised trial in major depression, 81 patients: 2 weeks, then 4 weeks of follow-up; Study: placebo-controlled trial, 55 outpatients: 5 or 10 days; Study: pilot trial, 52 patients: 5 days.
When effects appear: unknown; no source on this page gives a time to effect for Nemifitide. Results reported in the studies are under Published Research.
Source: Used in human trials, the duration of each row in Dosing Data below.
Side effects, and when to stop or get help
From the Side Effects section: Pain or redness at the injection site, mostly at 240 and 320 mg; no serious or significant systemic events in over 100 volunteers (PMID 11891671); Mild injection-site reactions that cleared within 24 hours with both needle and needle-free injection (PMID 16130176); In the 81-patient trial, side effects were as common on placebo and none led to dropout (PMID 16259645); No clinically significant side effects in the phase 2 extension (PMID 12974986). Full list and cautions ↓
When to stop or get help: unknown; no label or trial on file sets rules for stopping Nemifitide. Treat a severe or unexpected reaction as a reason to stop and see a doctor.
Source: the Side Effects section below (“From the trials carded above”).
Interactions
Unknown: a PubMed search for human interaction studies of Nemifitide (reviewed 2026-10-28) found none. Unknown is not the same as safe to combine.
Every peptide's record, with its source: the interaction matrix.
Checking what you bought
Unknown: no published independent test of Nemifitide products is in our lab-results database yet, so how products sold under this name measure up is not known.
To read a certificate of analysis, paste it into the COA decoder; it checks the measured mass against Nemifitide's expected mass, 694.8 Da, from this entry's molecular data. Trust & Verification explains what independent testing can and cannot show.
Legal status
US: Discontinued (Never approved: Drugs@FDA (openFDA) and the EMA medicines list hold no record, and ClinicalTrials.gov lists no trial (read October 28 and 29, 2026)). Sport: Prohibited (S0 catch-all).
Country by country ↓ · Regulatory tracker
Source: this entry's approval status and the WADA Prohibited List, as in Legal Status below.
Side Effects & Contraindications
Reported Side Effects
From the trials carded above.
Contraindications & Cautions
No approved label exists, so there are no official contraindications. Points from the studies:
Legal Status
Nemifitide was an investigational antidepressant and was never approved anywhere checked.
Frequently Asked Questions
?What is nemifitide?
A synthetic peptide of five amino acids, two of them chemically modified, developed by Innapharma as an antidepressant given by injection under the skin. Its development code was INN 00835.
?Did it work?
The evidence is limited. Small early trials reported fast, lasting improvement, mostly in patients with higher blood levels. In the largest randomised trial, 81 patients, 45 mg a day beat placebo at the point of peak effect; 30 mg was weaker. No phase 3 result was ever published.
?How can a drug with a 30-minute half-life have effects for weeks?
The trials did not explain it. Blood levels peak about 10 minutes after injection and fall quickly, yet improvements were reported to last weeks after short courses. That gap is one reason larger trials would have been needed.
?Is it approved?
No. Drugs@FDA and the EMA have no record of it, ClinicalTrials.gov lists no trial, and the last published study is from 2008.
?What doses were used in trials?
From 0.2 mg per kg or 18 mg a day in the early trials, 30 or 45 mg a day in the 2006 randomised trial, and 40 to 240 mg a day in an open study in treatment-resistant depression, always by subcutaneous injection. These are study amounts, not recommendations.
References
- [other] PubChem CID 6918348, Nemifitide: formula C33H43FN10O6, molecular weight 694.8. Read October 28, 2026. https://pubchem.ncbi.nlm.nih.gov/compound/6918348
- [clinical-trial] Feighner JP, et al. "Clinical pharmacokinetic studies with INN 00835 (nemifitide), a novel pentapeptide antidepressant." Biopharm Drug Dispos, 2002;23(1):33-9. PMID: 11891671.
- [clinical-trial] Nicolau G, et al. "Comparison of systemic exposure to nemifitide following two methods of subcutaneous administration to healthy volunteers." Biopharm Drug Dispos, 2005;26(9):379-85. PMID: 16130176.
- [clinical-trial] Kelly JP, et al. "The effect of treatment with a new antidepressant, INN 00835, on platelet serotonin uptake in depressed patients." J Affect Disord, 1999;55(2-3):231-5. PMID: 10628893.
- [clinical-trial] Feighner JP, et al. "A double-blind, placebo-controlled, efficacy, safety, and pharmacokinetic study of INN 00835, a novel antidepressant peptide, in the treatment of major depression." J Affect Disord, 2000;61(1-2):119-26. PMID: 11099750.
- [pubmed] Feighner JP, et al. "Cluster analysis of clinical data to identify subtypes within a study population following treatment with a new pentapeptide antidepressant." Int J Neuropsychopharmacol, 2000;3(3):237-242. PMID: 11343601.
- [clinical-trial] Feighner JP, et al. "Double-blind, placebo-controlled study of INN 00835 (netamiftide) in the treatment of outpatients with major depression." Int Clin Psychopharmacol, 2001;16(6):345-52. PMID: 11712623.
- [clinical-trial] Feighner JP, et al. "Clinical effectiveness of nemifitide, a novel pentapeptide antidepressant, in depressed outpatients: comparison of follow-up re-treatment with initial treatment." Int J Neuropsychopharmacol, 2003;6(3):207-13. PMID: 12974986.
- [clinical-trial] Montgomery SA, et al. "Efficacy and safety of 30 mg/d and 45 mg/d nemifitide compared to placebo in major depressive disorder." Int J Neuropsychopharmacol, 2006;9(5):517-28. PMID: 16259645.
- [clinical-trial] Feighner JP, et al. "Clinical effect of nemifitide, a novel pentapeptide antidepressant, in the treatment of severely depressed refractory patients." Int Clin Psychopharmacol, 2008;23(1):29-35. PMID: 18090505.
- [pubmed] Overstreet DH, et al. "Antidepressant-like effects of a novel pentapeptide, nemifitide, in an animal model of depression." Psychopharmacology (Berl), 2004;175(3):303-9. PMID: 14985919.
- [review] Dingemanse J. "Nemifitide. Innapharma." Curr Opin Investig Drugs, 2003;4(7):859-62. PMID: 14619408.
Sources & Citations
Studies were read from their PubMed abstracts on October 29, 2026; status from Drugs@FDA and ClinicalTrials.gov the same day and the EMA medicines list on October 28, 2026; formula and weight from PubChem. Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.