NMRA-335140

Navacaprant (NMRA-335140) was Neumora Therapeutics' lead program, an oral once-daily selective kappa-opioid receptor (KOR) antagonist for major depressive disorder [1][2]. The company ran three Phase 3 trials in parallel under the KOASTAL banner. All three missed their primary endpoint, the Montgomery-Asberg Depression Rating Scale (MADRS) change from baseline at Week 6, and Neumora discontinued the MDD program in June 2026, pairing the announcement with a roughly 35% workforce reduction [3][7]. KOASTAL-1 was disclosed in early January 2025 (LSMD 0.0 points, p=0.993) and cut Neumora's market cap by roughly 80% in a single session [6]. KOASTAL-2 (LSMD -0.3, p=0.813) and KOASTAL-3 (LSMD +0.7 favoring placebo, p=0.480) were released together on June 15, 2026 and confirmed that the compound did not separate from placebo rather than rescuing the first result [7]. For a company that went public in late 2023 almost entirely on the strength of this single asset, the readouts ended the standalone commercial thesis. A small Phase 2 study in bipolar II depression (NCT06429722, n=18) completed, but the primary MDD indication is closed [4].

Navacaprant is a novel chemical entity, never approved anywhere. Its highest clinical phase reached was Phase 3, where it failed. No FDA designations (breakthrough, fast track, orphan) were granted for the MDD indication. Three Phase 3 trials ran in parallel: KOASTAL-1 (NCT06029426, n=383), KOASTAL-2 (NCT06058039, n=422), and KOASTAL-3 (NCT06058013, n=430), each 6-week placebo-controlled studies in adults with MDD [1][2][3]. KOASTAL-1 topline (January 2, 2025) reported Week 6 MADRS change from baseline of -12.5 for navacaprant 80 mg versus -12.5 for placebo (LSMD 0.0, p=0.993); a prespecified female subgroup showed a nominal -2.7 LSMD (p=0.072), the only directional signal in the study [6]. Neumora kept the other two studies running on the hypothesis that patient selection or site-level placebo response had corrupted KOASTAL-1. The combined KOASTAL-2 and KOASTAL-3 readout on June 15, 2026 confirmed the first result: KOASTAL-2 MADRS CFB -12.2 (nav) vs -12.0 (pbo), LSMD -0.3, p=0.813; KOASTAL-3 MADRS CFB -10.1 vs -10.8, LSMD +0.7 (numerically favoring placebo), p=0.480 [7]. The company announced discontinuation of the MDD program and a ~35% workforce reduction concurrently [7]. A Phase 2 study in bipolar II depression (NCT06429722, n=18) completed enrollment, but Neumora has not committed to Phase 3 development in that indication [4]. The expected timeline for any regulatory submission in MDD is now null.

Most approved antidepressants work on monoamines (serotonin, norepinephrine, dopamine). Navacaprant does not. It blocks the kappa-opioid receptor (KOR), a protein on brain cells that normally receives signals from the body's own opioid-like molecules called dynorphins. When dynorphins bind KOR, the result is dysphoria, anhedonia (loss of pleasure), and in animal models, stress-induced depressive behavior. The therapeutic bet was simple: if an overactive dynorphin/KOR system drives the "nothing feels good" quality of depression, blocking the receptor should restore reward processing without touching serotonin at all. The genetic and pharmacological case for KOR antagonism in mood is suggestive but thin. Preclinical rodent data support it. Human data are weaker. Buprenorphine, which has partial KOR antagonism among several activities, has shown antidepressant signals, but its mu-opioid activity confounds any clean mechanistic read. Aticaprant (JNJ-67953964), Johnson & Johnson's selective KOR antagonist, failed its Phase 3 VENTURA program in MDD in 2024, the first large read of a pure KOR-antagonist mechanism in a well-powered registration study [9]. Navacaprant's three subsequent failures effectively close the book on selective KOR antagonism as monotherapy for broad MDD populations. The mechanism is not disproven for reward-deficit subtypes, treatment-resistant depression, or bipolar II depression, but no asset with pivotal-grade data remains to carry that hypothesis forward.

KOASTAL-1 (NCT06029426), KOASTAL-2 (NCT06058039), and KOASTAL-3 (NCT06058013) were 6-week randomized, double-blind, placebo-controlled studies in adults with MDD, with Week 6 change from baseline on the MADRS as the primary endpoint [1][2][3]. Enrollment totals were 383, 422, and 430 respectively. The comparator was placebo. Dose was 80 mg once daily. There was no active comparator arm. Design was conventional for an antidepressant registration package: three identical studies to buffer against the high placebo response that routinely sinks MDD trials. The Phase 3 program was built on an 8-week Phase 2a (NCT04221230, n~184) that technically missed its own primary endpoint: HAMD-17 change from baseline at Week 8 showed LSMD -1.7 (p=0.121) in the overall efficacy population [5][11]. Neumora initiated Phase 3 on the back of a prespecified moderate-to-severe subgroup (baseline HAMD-17 ≥22, n=100) that was statistically positive (LSMD -3.0, p=0.015) [11]. In hindsight, that is a thin basis for launching three parallel Phase 3 trials: the primary endpoint missed, the positive effect was concentrated in a severity-stratified slice, and HAMD-17 (Phase 2) and MADRS (Phase 3) are related but non-identical scales. The Phase 3 program also moved to MADRS and shortened to 6 weeks, so the Phase 2 signal was never directly re-tested on the Phase 3 endpoint. Running three parallel Phase 3 studies is defensible given MDD's noisy Phase 2 history, but it also meant Neumora could not course-correct between readouts. By the time KOASTAL-1 missed, KOASTAL-2 and -3 were already fully enrolled and reading out on the same mechanism, same dose, same endpoint, and same population definition. Running three identical trials maximizes the chance one hits by chance; it does not rescue a mechanism that is not working at the dose and population being tested. A 52-week open-label extension designed to feed long-term safety data into an eventual NDA became moot after the Phase 3 failures.

Our model estimates a 40% chance this drug is eventually approved. It starts from the historical base rate for Phase 3 drugs in this area (about 51%), then adjusts using ten facts about the trial and sponsor. What moves the number most: it is helped by a non-randomized design and its light or open-label blinding; it is held back by the sponsor's thin or weak approval record and weak or limited earlier-phase results. The other facts land near average for this stage, so they leave the estimate roughly where the base rate put it.

Efficacy risk was the one that killed it. MDD trials fail for reasons that are not always about the drug: placebo response rates of 30-45% are routine, enrollment captures a heterogeneous clinical phenotype, and the MADRS is a clinician-rated scale with its own noise. But three Phase 3 failures on the same compound, same dose, same endpoint, against separately enrolled populations, with LSMDs of 0.0, -0.3, and +0.7 (one numerically favoring placebo), is not a placebo-response story. It is a mechanism-doesn't-work-at-this-dose story, or it is a wrong-patients story, and Neumora did not retain the resources to run the follow-up that would distinguish between them. Safety was not the failure mode. Navacaprant was reasonably tolerated across the KOASTAL program; no on-target KOR signal (sedation, pruritus, GI effects) emerged at a program-ending level, and the KOASTAL-1 topline specifically noted no signal of increased suicidal ideation or behavior versus placebo [6][7]. Execution was mixed. Running three parallel Phase 3 trials is a defensible aggressive strategy when a mechanism is unproven, but it also meant Neumora continued burning cash on KOASTAL-2 and -3 after KOASTAL-1 missed, rather than redesigning for a narrower responder population or an enriched (moderate-to-severe only) enrollment that would have actually re-tested the Phase 2 subgroup hypothesis. Commercial risk is now moot for this indication. Even if the drug had scraped through on a borderline signal, payers would have demanded head-to-head data against generic SSRIs and SNRIs, which Neumora never had the capital to generate.

This is a tombstone, not a watch list item. The specific data point that would reopen the file is a positive Phase 2 readout from the bipolar II depression study (NCT06429722, completed), but with only 18 participants that trial is formally exploratory: it is powered to look for a safety and tolerability signal and perhaps a large preliminary efficacy signal, but it cannot distinguish a true drug effect from noise at any clinically meaningful effect size, and a nominally "positive" readout would need to be re-tested in a properly powered Phase 3 before meaning anything commercially [4]. Lay readers should not over-weight a bipolar II headline. Financially, Neumora went public in late 2023 on roughly a $2.5B valuation almost entirely on this asset; as of Q2 2026, market cap had collapsed to roughly $80M against $116.8M in cash and cash equivalents (i.e. the equity trades below cash) with runway into Q3 2027 after the 35% headcount cut [7][10]. The equity story has to be rebuilt around the back-of-pipeline programs, which per Neumora's post-discontinuation pipeline update are: **NMRA-511** (vasopressin 1a receptor antagonist, Phase 2 in Alzheimer's disease agitation), **NMRA-898** (M4 muscarinic positive allosteric modulator, Phase 1/early clinical in schizophrenia), and **NMRA-215** (NLRP3 inflammasome inhibitor, preclinical/early clinical in cardiometabolic disease) [7]. None of these are KOR-based or NMDA-based; the earlier characterization of Neumora as having an "NMDA receptor modulator" is not supported by the current public pipeline. No partner or acquirer has publicly expressed interest in the KOR antagonist mechanism or Neumora IP post-failure as of the Q2 2026 reporting cycle [10]. Check back if Neumora announces a strategic process (merger, asset sale, wind-down) or if any of the three remaining programs produce proof-of-concept data. For the broader bet on selective KOR antagonism in MDD, the active commercial story is over.