Research journey
Ketamine: 470 trials, 478 papers, one canvas
An anaesthetic from 1962 that became psychiatry’s fastest-acting antidepressant, an approved nasal spray, and a private clinic industry running well ahead of its own evidence. 470 trials, 478 papers, 59 of those trials stopped before they finished.
Milestones are curated from the Blossom research database. Registry completion dates are shown as planned; probability-weighted forecasts are part of Blossom Enterprise.
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The anaesthetic era
1962 to 1996Parke-Davis, battlefield medicine, paediatrics.1962
Parke-Davis
First synthesis at Parke-Davis
Calvin Stevens synthesises compound CI-581, a shorter-acting successor to phencyclidine.
Ketamine was not designed to treat anything psychiatric. Parke-Davis wanted an anaesthetic with phencyclidine’s pain control and fewer of its prolonged emergence problems, and CI-581 was the candidate that came out of that search.
Read the rest of this canvas against that origin. Every other compound in Blossom’s set is a molecule looking for an indication. Ketamine arrived with one, got approved for it, went into hospitals and field kits worldwide, and only found its psychiatric use nearly forty years later, from clinicians who already had it on the shelf.
That head start explains almost everything unusual about what follows: the generic pricing, the off-label clinic sector, and the awkward fact that the drug was widely available long before anyone ran a properly controlled depression trial on it.
1970
FDA approves Ketalar
Ketamine becomes a licensed general anaesthetic, and stays one everywhere in the world.
Approval as an anaesthetic is the single most consequential regulatory event on this canvas, and it happened five decades before anyone thought of it as an antidepressant.
It gave ketamine three things no other compound here has: a safety record accumulated across tens of millions of routine procedures, a supply chain of cheap generic vials, and a legal route for any licensed prescriber to use it off-label. Battlefield medicine and paediatric emergency care rely on it because it maintains blood pressure and airway reflexes where other anaesthetics do not.
It also created the problem. A drug already sitting in every hospital pharmacy can be given for depression tomorrow, without a single depression trial. Much of the tension in the lower half of this timeline comes from evidence trying to catch up with practice rather than lead it.
The antidepressant signal
1997 to 2015Berman and Zarate open a different question.1997
J Psychoactive Drugs
Ten years of ketamine psychedelic therapy
Evgeny Krupitsky reviews a decade of Russian work using ketamine as a psychotherapy adjunct for alcohol dependence.
Long before Western psychiatry took an interest, clinicians in Leningrad and later St Petersburg were using ketamine sessions alongside psychotherapy for alcohol dependence. This review pulls ten years of that work together.
It is easy to skip past, and worth not skipping. The addiction indication that Awakn and Solvonis are now running a Phase 3 on, three decades later, is not a new idea. It is an old idea that took thirty years to reach a trial design the regulators would accept.
1997-01
Yale University
Berman’s Yale crossover trial
Seven patients, a saline placebo, and depression scores falling within hours rather than weeks.
A tiny randomised, double-blind, placebo-controlled crossover pilot at Yale. Seven patients. Published in Biological Psychiatry in February 2000, it is now the most-cited paper in Blossom’s entire ketamine set at over 3,800 citations.
What made it startling was speed. Conventional antidepressants take four to six weeks to separate from placebo, and the field had largely accepted that as a property of how depression lifts. Ketamine moved scores within hours, which implied the delay was a property of the drugs, not the illness.
Hold two things at once here. This result reoriented an entire subfield and remains the origin point for everything below it on this canvas. It was also seven people in a crossover design, and a single small trial is a hypothesis rather than a finding. It took six more years for anyone to replicate it properly.
1998-01
Ketamine psychotherapy for heroin dependence
A double-blind dose-comparison trial in Leningrad, running in parallel with the first depression work.
Two-year follow-up data from a randomised trial in a treatment population Western research would not reach for another two decades. It ran at the same time as Berman’s Yale study, with no contact between the two.
Addiction and depression separated into different research lineages here and stayed separate. The addiction line goes quiet for years and only resurfaces in the 2020s with the UK alcohol programme further along this canvas.
1999
US Schedule III
Rising recreational use puts ketamine under federal control, but at a far lighter tier than the classic psychedelics.
Schedule III restricts, records and monitors. It does not block. Physicians can still prescribe, pharmacies can still stock, and researchers do not face the licensing burden that Schedule I imposes on psilocybin or 5-MeO-DMT.
This is the most under-appreciated reason ketamine has 470 trials in Blossom and every Schedule I psychedelic has a fraction of that. The regulatory friction is an order of magnitude lower, and volume of evidence follows friction more closely than it follows scientific promise.
2004-07
National Institute of Mental Health (NIMH)
NIMH opens the replication programme
Carlos Zarate’s intramural study runs for thirteen years and produces the trial that made the field believe.
The National Institute of Mental Health put its intramural programme behind replicating Berman, and the 2006 readout is the moment the antidepressant claim stopped being a curiosity. Government money, not industry money, did that work.
The registry record runs to 2017, which tells you something about how these programmes actually operate. It is a long-running platform study rather than a single readout, and the famous result comes from an early slice of it.
The economics here are worth stating plainly. Ketamine was already generic in 2004, so no company had a patent worth defending and no company was going to fund the pivotal work. Public funding filled the gap. When you reach the esketamine thread below, notice that the compound which attracted commercial development was the one that could be patented.
2008-02
Battlefield ketamine and PTSD
A study of burned service members finds lower PTSD rates among those who received ketamine during their care.
Ketamine’s haemodynamic stability (it does not drop blood pressure the way most anaesthetics do) made it standard in military and trauma medicine long before psychiatry noticed it. This retrospective study asked whether that incidental exposure left any psychiatric trace.
It is a correlation in a wounded population, not a trial, and the sickest patients get different anaesthetics for reasons that also predict PTSD. A later retrospective in 274 war-wounded soldiers is also in Blossom’s set and complicates the picture rather than confirming it.
Kept here because it shows the actual sequence: the signal came from noticing something in routine care, and the trials followed.
2010-08
Archives of General Psychiatry
Randomised add-on trial in bipolar depression
The NIMH group extends the finding past unipolar depression, in Archives of General Psychiatry.
Bipolar depression is harder to treat and easier to destabilise, because antidepressants can tip some patients into mania. Showing a rapid effect there, in a randomised add-on design, widened the claim considerably.
A replication in Biological Psychiatry followed in 2012. Two independent randomised results in the harder population is a meaningfully stronger position than one, and this is roughly the point at which clinicians outside research settings started asking how to get hold of it.
2013-10
American Journal of Psychiatry
Two-site randomised controlled trial
Murrough and colleagues run the first multi-site RCT, using midazolam rather than saline as the comparator.
The comparator is the point. Saline placebo is useless against a drug that produces obvious dissociation within minutes, because everyone in the room can tell who got what. Midazolam produces sedation, so it gives the blind a fighting chance.
This trial is where ketamine research started taking its own blinding problem seriously, and the answer held: the effect survived an active comparator. It is also the design that the suicidality trials later built on.
Approval and sprawl
2016 to 2023Spravato, and a clinic industry running ahead of its evidence.2016-05
Nature
The metabolite result, in Nature
Zanos and colleagues report antidepressant actions from a ketamine metabolite that does not block the NMDA receptor.
For sixteen years the explanation had been NMDA receptor blockade (ketamine switching off a particular glutamate receptor). This paper argued that hydroxynorketamine, a downstream metabolite, produced antidepressant effects in mice without doing that at all.
If it holds, it means the therapeutic effect and the dissociation can be separated, and every company on this canvas trying to build a non-dissociating ketamine has a mechanistic story to point at. Blossom’s set has it at over 1,500 citations, second only to Berman.
It has not gone unchallenged. Replication has been contested and the field has not settled, which is a useful reminder that a Nature paper is a strong claim rather than a closed question. Gilgamesh’s GluN2B-selective programme and Ketabon’s dissociation-free oral formulation are both, in effect, bets on this line of reasoning being right.
2016-09
ended earlyAbuse potential and use disorder
A review sets out what repeated ketamine exposure does when it is not carefully controlled.
Ketamine has a well-documented recreational user base and a well-documented pattern of harm at high frequency: cognitive effects, and a distinctive and sometimes irreversible bladder pathology in heavy long-term users.
Nothing in the therapeutic literature suggests supervised infusion protocols produce that. But the maintenance question is real and largely unanswered. Patients who respond usually relapse within weeks, so treatment becomes repeated dosing over months or years, and the trials that established efficacy ran for four weeks.
Put this next to the clinic sector further down and the gap is obvious: the safety evidence covers a course of treatment, while a lot of real-world use is open-ended.
2017-07
Lancet Psychiatry
ended earlySide effects systematic review
Lancet Psychiatry pools the adverse-event data across depression trials.
Systematic reviews of harms are the least glamorous documents in any evidence base and usually the most useful. Individual trials are too small to catch anything uncommon; pooling is the only way to see it.
Published alongside a consensus statement in JAMA Psychiatry the same year, in which a group of clinicians tried to set out what responsible off-label use should look like. Both documents exist because prescribing was already happening at scale and the field was trying to put guard rails around practice it could no longer slow down.
2018-07
Tasman Therapeutics
ended earlyFirst R-107 bioavailability study withdrawn
The oral extended-release programme’s opening study never enrols. A second attempt in 2022 is also withdrawn.
Two registered bioavailability studies for the same tablet, four years apart, both withdrawn before enrolling anyone. Registered intent and delivered research are different quantities, and this thread starts by demonstrating it.
The programme recovered and is now the furthest advanced oral ketamine in development. Kept on the canvas because the recovery is only legible if the false starts are visible too.
2019-03
Janssen Pharmaceuticals
FDA approves Spravato
Esketamine nasal spray is cleared for treatment-resistant depression, the first genuinely new antidepressant mechanism in decades.
Janssen took the S-enantiomer (one of the two mirror-image halves of the racemic molecule), delivered it intranasally, and got the patent protection that racemic ketamine could never offer. That is the whole commercial logic of the programme, and it worked.
Approval came with a REMS: administration in a certified clinic, two hours of monitoring after every dose, no take-home supply. Those conditions are why nearly every entry on the oral and at-home thread below exists. Removing the monitoring requirement is the prize the reformulators are chasing.
A 2020 expansion added major depressive disorder with acute suicidal ideation, on the back of the ASPIRE studies. Approval on a suicidality endpoint was itself a first, and it changed what regulators were willing to accept as a registrational outcome.
The awkward question the rest of this canvas keeps returning to: Spravato is expensive and clinic-bound, while generic racemic ketamine is cheap and, on the available comparisons, works about as well. Nobody has yet run the trial that settles it. One is now underway.
2020-05
Janssen Pharmaceuticals
ASPIRE I and II report
Two Phase 3 studies in major depression with active suicidal ideation and intent.
Trials in actively suicidal patients are rare, because ethics committees are cautious and sponsors are more cautious still. Running two of them was a real commitment.
Both showed rapid reduction in depressive symptoms. Neither demonstrated a durable effect on suicidality itself, which is the outcome the indication is named after, and that distinction is often lost when the approval gets summarised.
2022-01
American Journal of Psychiatry
KARE reports in alcohol use disorder
96 patients, ketamine plus a targeted therapy protocol, 86% abstinence at six months.
One of the largest effect sizes reported in alcohol use disorder treatment, from a UCL trial pairing ketamine with therapy aimed at reward memories. Relapse risk came out 2.7 times lower than control.
Effect sizes that large in a small trial should raise an eyebrow as well as hopes; they shrink more often than they hold. The result was strong enough to attract MRC and NIHR co-funding for a Phase 3, which is the appropriate response to a promising small trial.
2022-08
Freedom Biosciences
Freedom Biosciences raises $10.5m
A Yale spinout co-founded by John Krystal emerges from stealth to try to make ketamine’s effect last longer.
The premise is narrow and sensible: ketamine works quickly and wears off within about a week, so combine it with an mTOR inhibitor and see whether the window stretches. FDA cleared the IND in 2024 and a roughly 100-patient Phase 2a followed.
Duration, not onset, is ketamine’s real clinical problem. A treatment that requires indefinite repeat dosing is a different proposition from one that produces lasting remission, and almost none of the money on this canvas is aimed at that gap.
2022-10
The clinic and telehealth sector arrives at scale
Large open-label and retrospective datasets from commercial infusion clinics and at-home sublingual telehealth providers.
By 2022 the private sector was treating far more people with ketamine than every registered trial combined, and it started publishing. A prospective open-label telehealth study of at-home sublingual ketamine, a retrospective series from off-label at-home use, and a chart review from a large community infusion practice all landed within weeks of each other.
This is genuinely contested territory and worth being precise about. The data are real, the cohorts are large, and the reported outcomes are broadly favourable. They are also uncontrolled, self-selected, commercially generated, and measured mostly in the first weeks of treatment. Open-label depression data flatter almost any intervention.
The honest position is neither dismissal nor endorsement. A sizeable industry is delivering an off-label treatment to people whom the licensed system has often failed, at a price point Spravato cannot match, using a legal route that has existed since 1970. It is running ahead of the controlled evidence, and it is producing the only large-scale real-world data anyone has. Both of those are true.
The question that matters is not whether clinics should exist. It is what happens at month twelve, and almost nothing on this canvas answers that.
2023-04
ended earlyHarms reporting reviewed
A systematic review finds adverse-event reporting in the esketamine trial programme incomplete.
The reviewers went back through the registration trials and asked a narrow question: were harms reported in enough detail to be assessed independently? The answer was no, not consistently.
This is a criticism of reporting practice rather than a claim that the drug is unsafe, and the two get conflated easily. But it matters for a product whose approval rested on a defined benefit-risk balance, and it is the sort of finding that never appears in a company timeline.
2023-06
NEJM
ELEKT-D: ketamine against electroconvulsive therapy
In non-psychotic treatment-resistant depression, ketamine is non-inferior to ECT, published in the NEJM.
ECT is the most effective treatment psychiatry has for severe depression and the one patients most often refuse, because of the anaesthesia, the stigma and the memory effects. Matching it is a serious claim.
Blossom’s record shows the trial running from July 2017 to December 2022. Alongside the Australian KADS trial of repeated subcutaneous injections published three weeks later, 2023 was the year ketamine acquired properly powered comparative evidence rather than more small placebo trials.
The caveats are specific: non-psychotic patients only, an open-label design, and non-inferiority rather than superiority. It shows ketamine is a reasonable alternative for a defined group, not that it replaces ECT.
2023-08
Ketabon
ended earlyKET01 misses its primary endpoint
Ketabon’s oral prolonged-release ketamine separates from placebo at day four and seven, then fails at day twenty-one.
122 patients across 29 sites in Germany, Poland and the Czech Republic. Strong early signal, no statistical significance at the day-21 primary endpoint. On the pre-specified terms the sponsor set itself, the study failed.
The company’s counter-argument is the dissociation data: a CADSS score of 0.7 against 29.6 for Spravato in a later head-to-head. If antidepressant effect really can be had without dissociation, the two-hour monitoring requirement that constrains Spravato falls away, and the commercial picture changes completely.
That is a genuine bet, not spin, and it rests on the metabolite line of reasoning from 2016. It also has not yet been demonstrated on a primary endpoint.
2023-10
New England Journal of Medicine
ESCAPE-TRD beats quetiapine
A head-to-head against an established augmentation drug, published in the New England Journal of Medicine.
Esketamine plus an antidepressant outperformed quetiapine extended-release plus an antidepressant on remission at week eight. Beating an active comparator that guidelines already recommend is a stronger claim than beating placebo.
It is open-label, which for a drug producing obvious dissociation is a real limitation rather than a technicality. Long-term extension data followed in 2026, and the economic analyses that came after it are the ones payers actually read.
2023-10
Nature Mental Health
ended earlyKetamine masked by surgical anaesthesia: no difference
Given to patients already unconscious for surgery, so nobody could tell who received it, ketamine did not beat placebo.
The cleverest trial design on this canvas, and the most uncomfortable result. Patients undergoing surgery were randomised to ketamine or placebo while already under general anaesthesia, which makes the blind genuinely airtight. Neither patients nor raters could tell.
Both groups improved substantially. Neither improved more than the other.
One interpretation is that a meaningful part of ketamine’s antidepressant effect in ordinary trials comes from expectation, made powerful by the unmistakable experience of having received something. Another is that a patient who is unconscious cannot have the experience that does the therapeutic work. A third is that the trial was small, in a surgical population, and does not generalise.
Nobody knows which is right, and a 2026 systematic review of blinding integrity across psychedelic trials suggests the problem is not confined to ketamine. This is the strongest existing challenge to the whole edifice above it, so it belongs here at full weight rather than in a footnote.
Sorting it out
2024 onwardsHead-to-head trials and the oral formulation question.2024-03
NRx Pharmaceuticals
NRX-101 hits one endpoint and misses the other
A 58% reduction in time to sustained remission from suicidality, and no differentiation on the antidepressant endpoint.
The suicidality result reached p=0.05, and akathisia (a distressing inner restlessness that independently raises suicide risk) fell by 76%. The primary antidepressant endpoint did not separate.
Whether that is a success depends entirely on which endpoint you think the drug is for. NRx is pursuing suicidality as a registrational claim, and a 2018 Breakthrough Therapy Designation suggests the FDA is open to it.
Mixed results are the most common outcome in psychiatry trials and the least often shown on timelines. This one is here as it stands, with both halves.
2024-06
Tasman Therapeutics
BEDROC reports in Nature Medicine
Extended-release ketamine tablets taken unsupervised at home beat placebo in treatment-resistant depression.
231 patients randomised. The 180mg dose showed a six-point MADRS separation from placebo, relapse at 42.9% against 70.6%, and over 96% compliance with at-home dosing. Minimal dissociation reported.
If it replicates, this is the result that unpicks the delivery model the whole field is built around. No clinic, no infusion chair, no two-hour monitoring window, no session staffing cost. The barrier to ketamine has never mostly been the molecule.
One randomised Phase 2 is a beginning. The Phase 3 programme that followed it is what will decide the question.
2024-08
Solvonis Therapeutics
MORE-KARE Phase 3 opens in the NHS
The first Phase 3 of ketamine-assisted therapy for alcohol use disorder, co-funded by MRC and NIHR at about £2.4m.
Around 280 patients across seven or eight NHS trusts. Public co-funding matters here for the same reason it mattered at NIMH twenty years earlier: generic ketamine has no patent to defend, so someone other than a sponsor has to pay for the pivotal work.
Running inside the NHS also means the evidence lands directly where a commissioning decision would be made, rather than needing to be translated into a different health system afterwards.
2024-12
ended early59 trials stopped before they finished
Across the 470 ketamine trials in Blossom, 59 are terminated or withdrawn. Adolescents, postpartum depression and emergency settings recur.
One in eight registered ketamine trials never reached a result. Yale terminated a study of severe adolescent depression, Columbia stopped a paediatric suicidality infusion trial, and several emergency-department suicidality studies ended early at military and academic sites.
Registries rarely record why. Recruitment failure, funding, and strategic reprioritisation are as common as safety or futility, and a terminated study looks identical to a failed one in the record.
The pattern is worth noticing anyway. Adolescents, postpartum patients and acutely suicidal people in emergency departments are exactly the populations where a fast-acting antidepressant would matter most, and they are the populations where these trials most often collapsed.
2025-02
Solvonis Therapeutics
Awakn is acquired by Solvonis
A roughly 53.5% premium at about C$0.146 a share, with the combined company on the London Stock Exchange.
A premium on a very low share price is still a very low share price. Awakn had a Phase 3 in the field and needed capital it could not raise alone, and the acquisition provided a listing and a balance sheet.
This is the custody change on the alcohol thread, and it is a more typical psychedelics-sector outcome than the headline acquisitions get: not a pharma buyout at scale, but a small-cap absorbing a smaller one to keep a trial funded.
2025-04
Tasman Therapeutics
ROCKET Phase 3 opens, funding not yet closed
The pivotal programme for oral ketamine begins enrolling, against an announced $175m Series A that has not closed.
Enrolment across US and international sites from the second half of 2025, with FDA submission targeted for 2027. The company has announced a $175m Series A to fund it, which would be the largest raise in ketamine therapeutics.
Announced is not closed. A Phase 3 that begins before its funding is secured is a normal biotech gamble and a real risk to the readout, and it is the sort of detail a pipeline chart drops.
2025-08
PharmaTher
KETARx approved, after two rejections
PharmaTher wins ANDA approval for a ketamine injection in surgical pain, following complete response letters in April and October 2024.
Two rejections before approval, both on manufacturing rather than science. Generic approvals turn on whether you can make the product reliably, and that is where small companies most often come unstuck.
US commercialisation rights were sold in December 2025 for a deal potentially worth over $25m, funding the company’s Parkinson’s programme. Selling the approval to fund the next thing is the standard route for a company this size, and it is one of the few clean money events on this canvas.
2025-10
Five years of real-world safety
The post-approval safety picture, assembled from routine use rather than trial conditions.
Five years and a large exposed population is the point at which a post-marketing safety analysis starts being able to say something trials cannot. Rare events need volume.
It arrived alongside a randomised trial of esketamine as monotherapy, without the oral antidepressant it was originally approved to be added to. The FDA had already cleared that use in January 2025, so the trial reads as evidence catching up with a licensed indication rather than opening a new one. The evidence base is still growing after approval, which is how it should work and is not always how it goes.
2026-06
At-home subcutaneous ketamine, observed at scale
A large heterogeneous US cohort receiving telehealth-supported subcutaneous ketamine for depression, anxiety and PTSD.
The sector keeps moving up the route-of-administration ladder. Sublingual lozenges gave way to supervised subcutaneous injection at home, which is closer to clinical dosing and further from anything a regulator has reviewed.
Observational, uncontrolled, and from a provider with an interest in the answer. Read it as a description of what is happening rather than evidence about whether it works.
2026-06
JAMA Network Open
Two randomised trials of oral prolonged-release ketamine
JAMA Network Open publishes the paired randomised evidence on the oral formulation.
Two randomised clinical trials reported together in a major journal. This is the most complete published test of whether a swallowed, take-home ketamine can do what an infusion does.
It lands a month before the point this canvas stops, and it is the single most consequential open item in the near term. If oral works, Spravato’s clinic-bound model and the entire infusion clinic sector are both competing with a tablet.
The paper is new enough that citation and replication have not caught up with it, so treat the readout as the beginning of an argument rather than its conclusion.
2026-07
The cost gap, measured
Real-world effectiveness and cost of intranasal esketamine against intramuscular generic ketamine, side by side.
The comparison the field has been avoiding since 2019, done on routine care data: one branded, approved, clinic-bound product against one cheap generic given by injection.
Retrospective comparisons cannot settle it, because the patients who end up on each are not alike. But the economic asymmetry is large enough that payers were always going to ask, and the earlier US cost-effectiveness modelling pointed the same way.
2026-09
NRx Pharmaceuticals
plannedNRX-100 full NDA expected
A rolling filing for IV ketamine in suicidal depression, built on a real-world dataset of more than 70,000 patients.
Sections have been going to the FDA since December 2024 under a rolling review, with Fast Track granted in August 2025 and the dataset confirmed at a Type C meeting in March 2026.
The interesting part is the evidence base. This is an attempt to get a generic anaesthetic formally approved for a psychiatric indication largely on real-world data rather than new trials, which if it works is a template a lot of off-patent medicine would want to copy.
The date here is the sponsor’s guidance, not a regulatory commitment, and filing guidance slips routinely.
2027-06
plannedenterpriseProbability-weighted scenarios across the ketamine field
Filing timing, approval probability and payer response modelled across the oral, esketamine and off-label routes.
Everything else on this canvas is public record: registry entries, published papers, filed announcements.
Blossom Enterprise models what happens when a generic anaesthetic, a patented nasal spray and an at-home tablet compete for the same patients, which is the analysis that turns a timeline into a decision. It is the one marker here you cannot verify from a registry.
2030-12
Yale University
plannedSpravato against generic ketamine, at last
A PCORI-funded equivalence study at Yale, running to the end of 2030.
The question everything else on this canvas has been circling since 2019, finally put to a trial: does the approved branded product actually outperform the cheap generic it was derived from?
It is publicly funded, because no company has any reason to run it. Whichever way it lands, one side loses something. If equivalence holds, the case for a premium clinic-administered product weakens sharply. If it does not, a large off-label industry is giving people a second-best treatment.
The completion date is 2030, which means this argument continues for another four years regardless of what anyone publishes in the meantime.
2031-09
Johnson & Johnson
plannedAVENUE completes
J&J’s Phase 3 pushing esketamine beyond treatment-resistant depression into major depressive disorder generally.
Recruiting since January 2026, with a registry completion date in late 2031. Moving from treatment-resistant depression into MDD generally means a far larger eligible population and a far harder efficacy comparison, because most of those patients have untried conventional options.
It is also the furthest point on this canvas: twelve years after approval, the company that got there first is still expanding the label.
Ketamine
The one that made it: a research journey