ATX-304 (formerly O304)

ATX-304 is an experimental oral small molecule. A 23-person phase 1b study reported an 8% mean rise in resting metabolic rate and minimal weight loss; the same abstract’s 33% figure was an ‘up to’ value. No placebo-adjusted body-weight effect was reported.

Investigational oral small-molecule AMPK network activator

Former development name O304
Oral small molecule
ATX-304 sodium tablets differ from the earlier O304 suspension

What is ATX-304, and is O304 the same product?

ATX-304 is an investigational small molecule intended to activate the AMPK network indirectly. O304 is the earlier development name, but the published TELLUS study used an O304 oral suspension while later work used ATX-304 sodium tablets. Results should not be transferred across formulations without exposure bridging.

A rename can preserve the active-moiety program while formulation, salt, dose, and exposure still change.

TELLUS · 28-day human proof of concept

Randomized trial with preclinical program

Steneberg et al., JCI Insight, 2018

In a 65-person proof-of-concept trial, O304 was studied for glucose, insulin resistance, blood pressure, and microvascular perfusion on top of metformin.

Participants / model: Adults with type 2 diabetes taking metformin
Treatment: Oral O304 suspension or placebo
Follow-up: 28 days
Study design: Randomized phase 2a proof-of-concept trial embedded in a mechanistic report
Funding: Betagenon-linked investigators

Short duration, selected analyses, and a suspension formulation limit transfer to weight loss or ATX-304 tablets.

Read the original source

ATX-304 phase 1b · metabolic signals

Conference abstract

Thieroff-Ekerdt et al., Diabetes, 2026

In 23 participants randomized 2:1, the abstract reports within-baseline adiponectin, MRI fat, and resting-metabolic-rate changes but no between-group weight-loss effect.

Participants / model: Adults with obesity and prediabetes
Treatment: ATX-304 400 mg daily or placebo
Follow-up: 8 weeks plus optional 8-week open-label extension
Study design: Randomized phase 1b trial reported as a conference abstract
Funding: Cambrian Biopharma

The abstract says up to 33% for resting metabolic rate but does not provide the mean, comparator difference, or uncertainty.

Read the original source

Is ATX-304 approved or available as a medicine?

FDA approval records contained no exact-name ATX-304 or O304 entry. The 2026 human report is a conference abstract, and the developer says larger phase 2 studies are planned.

Planned phase 2 studies are not evidence that a dose reduces body weight.

FDA records · ATX-304 status

Regulatory database record set

FDA Drugs@FDA and openFDA records

The cited U.S. approval records contain no exact-name ATX-304 or O304 entry.

Participants / model: United States drug approvals
Treatment: ATX-304 and O304
Study design: Exact-name U.S. approval coverage

Read the original source

ATX-304 phase 1b · metabolic signals

Conference abstract

Thieroff-Ekerdt et al., Diabetes, 2026

In 23 participants randomized 2:1, the abstract reports within-baseline adiponectin, MRI fat, and resting-metabolic-rate changes but no between-group weight-loss effect.

Participants / model: Adults with obesity and prediabetes
Treatment: ATX-304 400 mg daily or placebo
Follow-up: 8 weeks plus optional 8-week open-label extension
Study design: Randomized phase 1b trial reported as a conference abstract
Funding: Cambrian Biopharma

The abstract says up to 33% for resting metabolic rate but does not provide the mean, comparator difference, or uncertainty.

Read the original source

What did the first O304 human trial actually measure?

TELLUS randomized 65 adults with type 2 diabetes taking metformin to O304 or placebo for 28 days. The paper reported changes in fasting glucose, insulin-resistance measures, blood pressure, and microvascular perfusion, but this was a short diabetes proof-of-concept study, not a weight-loss trial.

The published figures show 25 O304 and 24 placebo participants in key glucose analyses. Several perfusion findings came from baseline-defined subgroups or within-group comparisons.

TELLUS · 28-day human proof of concept

Randomized trial with preclinical program

Steneberg et al., JCI Insight, 2018

In a 65-person proof-of-concept trial, O304 was studied for glucose, insulin resistance, blood pressure, and microvascular perfusion on top of metformin.

Participants / model: Adults with type 2 diabetes taking metformin
Treatment: Oral O304 suspension or placebo
Follow-up: 28 days
Study design: Randomized phase 2a proof-of-concept trial embedded in a mechanistic report
Funding: Betagenon-linked investigators

Short duration, selected analyses, and a suspension formulation limit transfer to weight loss or ATX-304 tablets.

Read the original source

What did the 2026 ATX-304 phase 1b abstract show?

Twenty-three adults with obesity and prediabetes were randomized 2:1 to 400 mg daily or placebo for eight weeks, followed by an optional open-label extension. The abstract reports higher adiponectin and lower MRI-measured liver and visceral fat versus baseline, but it does not present a placebo-adjusted body-weight effect.

The developer later said weight loss was minimal at this exposure. This directly limits the claim that human weight-loss efficacy has been shown.

ATX-304 phase 1b · metabolic signals

Conference abstract

Thieroff-Ekerdt et al., Diabetes, 2026

In 23 participants randomized 2:1, the abstract reports within-baseline adiponectin, MRI fat, and resting-metabolic-rate changes but no between-group weight-loss effect.

Participants / model: Adults with obesity and prediabetes
Treatment: ATX-304 400 mg daily or placebo
Follow-up: 8 weeks plus optional 8-week open-label extension
Study design: Randomized phase 1b trial reported as a conference abstract
Funding: Cambrian Biopharma

The abstract says up to 33% for resting metabolic rate but does not provide the mean, comparator difference, or uncertainty.

Read the original source

What does the 33% resting-metabolic-rate figure mean?

The conference abstract says resting metabolic rate increased by up to 33% from baseline. A developer disclosure for the same study reports an 8% mean increase. Neither report supplies the full arm-level distribution or a placebo-adjusted estimate.

The 33% value appears to be a maximum or selected within-person change, not the group mean. It should not be advertised as the expected effect.

ATX-304 phase 1b · metabolic signals

Conference abstract

Thieroff-Ekerdt et al., Diabetes, 2026

In 23 participants randomized 2:1, the abstract reports within-baseline adiponectin, MRI fat, and resting-metabolic-rate changes but no between-group weight-loss effect.

Participants / model: Adults with obesity and prediabetes
Treatment: ATX-304 400 mg daily or placebo
Follow-up: 8 weeks plus optional 8-week open-label extension
Study design: Randomized phase 1b trial reported as a conference abstract
Funding: Cambrian Biopharma

The abstract says up to 33% for resting metabolic rate but does not provide the mean, comparator difference, or uncertainty.

Read the original source

ATX-304 sponsor update · mean RMR and weight

Sponsor disclosure

Cambrian Biopharma, June 18, 2026

The developer reports an 8% mean resting-metabolic-rate rise, minimal weight loss, and mostly mild adverse events in the 23-person study.

Participants / model: Same 23-person phase 1b cohort
Treatment: ATX-304 400 mg daily or placebo
Follow-up: 8 weeks plus open-label extension
Study design: Sponsor summary of conference data

The press release is useful for reconciling the abstract but is not peer-reviewed and omits full arm-level data.

Read the original source

Is an 11-hour half-life established in people?

The cited human records do not report that number as a terminal half-life. The 11-hour estimate came from interpreting an animal-study graph. Human dosing frequency and exposure in trial records do not substitute for a reported human half-life.

The human terminal half-life remains unreported. The approximate 11-hour value came from an animal graph.

ATX-304 phase 1b · metabolic signals

Conference abstract

Thieroff-Ekerdt et al., Diabetes, 2026

In 23 participants randomized 2:1, the abstract reports within-baseline adiponectin, MRI fat, and resting-metabolic-rate changes but no between-group weight-loss effect.

Participants / model: Adults with obesity and prediabetes
Treatment: ATX-304 400 mg daily or placebo
Follow-up: 8 weeks plus optional 8-week open-label extension
Study design: Randomized phase 1b trial reported as a conference abstract
Funding: Cambrian Biopharma

The abstract says up to 33% for resting metabolic rate but does not provide the mean, comparator difference, or uncertainty.

Read the original source

Does phase 1b establish that ATX-304 is safe?

No. The 23-person abstract and sponsor disclosure describe mostly mild events and no signal in monitored temperature or 24-hour heart rate, but such a small study cannot characterize rare toxicity, longer exposure, interactions, or safety at doses intended to produce weight loss.

ATX-304 phase 1b · metabolic signals

Conference abstract

Thieroff-Ekerdt et al., Diabetes, 2026

In 23 participants randomized 2:1, the abstract reports within-baseline adiponectin, MRI fat, and resting-metabolic-rate changes but no between-group weight-loss effect.

Participants / model: Adults with obesity and prediabetes
Treatment: ATX-304 400 mg daily or placebo
Follow-up: 8 weeks plus optional 8-week open-label extension
Study design: Randomized phase 1b trial reported as a conference abstract
Funding: Cambrian Biopharma

The abstract says up to 33% for resting metabolic rate but does not provide the mean, comparator difference, or uncertainty.

Read the original source

ATX-304 sponsor update · mean RMR and weight

Sponsor disclosure

Cambrian Biopharma, June 18, 2026

The developer reports an 8% mean resting-metabolic-rate rise, minimal weight loss, and mostly mild adverse events in the 23-person study.

Participants / model: Same 23-person phase 1b cohort
Treatment: ATX-304 400 mg daily or placebo
Follow-up: 8 weeks plus open-label extension
Study design: Sponsor summary of conference data

The press release is useful for reconciling the abstract but is not peer-reviewed and omits full arm-level data.

Read the original source

Studies and sources

FDA records · ATX-304 status

Regulatory database record set

FDA Drugs@FDA and openFDA records

The cited U.S. approval records contain no exact-name ATX-304 or O304 entry.

Participants / model: United States drug approvals
Treatment: ATX-304 and O304
Study design: Exact-name U.S. approval coverage

Read the original source

TELLUS · 28-day human proof of concept

Randomized trial with preclinical program

Steneberg et al., JCI Insight, 2018

In a 65-person proof-of-concept trial, O304 was studied for glucose, insulin resistance, blood pressure, and microvascular perfusion on top of metformin.

Participants / model: Adults with type 2 diabetes taking metformin
Treatment: Oral O304 suspension or placebo
Follow-up: 28 days
Study design: Randomized phase 2a proof-of-concept trial embedded in a mechanistic report
Funding: Betagenon-linked investigators

Short duration, selected analyses, and a suspension formulation limit transfer to weight loss or ATX-304 tablets.

Read the original source

ATX-304 phase 1b · metabolic signals

Conference abstract

Thieroff-Ekerdt et al., Diabetes, 2026

In 23 participants randomized 2:1, the abstract reports within-baseline adiponectin, MRI fat, and resting-metabolic-rate changes but no between-group weight-loss effect.

Participants / model: Adults with obesity and prediabetes
Treatment: ATX-304 400 mg daily or placebo
Follow-up: 8 weeks plus optional 8-week open-label extension
Study design: Randomized phase 1b trial reported as a conference abstract
Funding: Cambrian Biopharma

The abstract says up to 33% for resting metabolic rate but does not provide the mean, comparator difference, or uncertainty.

Read the original source

Why is ATX-304 (formerly O304) in B tier?

B reflects a 65-person, 28-day diabetes trial and a 23-person, eight-week obesity and prediabetes study with measurable metabolic effects. Neither study established weight-loss efficacy or safety at weight-loss doses.