SRK-439 dosage and evidence
Written by Aaron CuhaReviewed Sep 2026
The short answer
SRK-439 is Scholar Rock's follow-up to apitegromab, built to be self-injected alongside GLP-1 drugs. First results in people are expected in the second half of 2026.
Evidence grade for SRK-439: Animal or lab only. The rule: only animal or lab studies on this page. No study in people yet. The sum on this page: 1 animal study, no human study. A grade counts how much has been done to people, not whether it works.
- People given it
- 0
- Human studies
- 0
- Found nothing
- 0
Dose
No human dose established
No published study on this page has given this compound to people and reported a result.
1 animal study, no human study
1 effects reported, 1 unwanted, by people using it, not a trial
In plain English
In plain English, from Aaron
This is how I would explain it to a friend. The evidence, with the numbers, is further down the page.
SRK-439 is an antibody shot from Scholar Rock that blocks myostatin, a brake on muscle. It is built to be self-injected by people on GLP-1 drugs. It is at an early stage and not approved.
What people take it for
- Keeping muscle on GLP-1 drugs.
- Less weight regain after stopping a GLP-1 drug.
What studies in people showed
Nobody has published results in people. A first safety study in healthy volunteers is under way, with results due in the second half of 2026. In primates, lean mass went up at every dose. In mice, fat came back less after a GLP-1 drug was stopped.
What people report
Reports, not study results
The good
- We have not collected user reports on this one yet.
The bad
- No results or side effect data in people have been published yet.
Where these come from: Everything here is from the company updates on this page. There are no user reports.
My bottom line
Animal data only. The muscle saver that works today is lifting.
An opinion, not a finding. I am a coach, not a doctor.
What it has been measured to do
Nothing indexed yet
The 2 citations on this page do not report a result for any of the 36 goals indexed here. Most of what sits here is something else: a listing of a planned study, a study of how the body handles the drug, a safety report or a government record. None of those tests whether it works.
Show full evidence
What is SRK-439?
SRK-439 is Scholar Rock's follow-up to apitegromab, built to be self-injected alongside GLP-1 drugs. First results in people are expected in the second half of 2026.
SRK-439 blocks the same inactive form of myostatin as apitegromab. Apitegromab is given through a drip for spinal muscular atrophy. SRK-439 is built as a shot under the skin that people give themselves, for obesity. The goal is to save muscle during GLP-1 treatment and to slow weight regain afterwards. There is no data in people yet. A first safety study in healthy volunteers is under way, with results expected in the second half of 2026. In primates, lean mass went up at every dose tested. In mice, fat came back less after a GLP-1 drug was stopped.
How does SRK-439 work?
It is an antibody that stops myostatin from switching on.
The evidence, in charts
Fig. 1a · how many people
0people have taken this in any study cited here
0 people · 0 studies in people
What this page cites instead is 1 animal study and 1 review. None of them gave the compound to a person.
Counted from the list of sources on this page. We draw this chart only when a study in people is cited. An empty one is the answer, not a gap in the page.
Fig. 1b · evidence mix
None of the 2 sources here are studies in people.
- Animal study · done in animals150%
- Review of studies · sums up other studies150%
Counted from the list of sources on this page. It counts only what we cite, so there may be more studies out there. A review counts once, however many studies it sums up.
Fig. 2 · evidence over time
Sources here come from just two years, 2025 and 2026.
Too few different years on this page to draw a timeline.
Fig. 3 · legal status at a glance
US
Not approved
UK
Not approved
AU
Not approved
CA
Not approved
Not approved in any of the four countries shown. This is what the law says, not a verdict on the science. See Legal status below for the full text and any notes.
Fig. 4 · how much does what
Nobody has tested different amounts in people
This chart would show how the effect changes as the amount goes up. For this compound, nobody has measured that in people. So we leave it empty. We will not borrow an animal chart and pretend it works the same in people.
Fig. 5 · what the molecule is
- Kind of compound
- Biologic
- Molecule weight
- Not disclosed
- Half-life
- Stated in words, not a numbersee the exact wording below
- Chain length
- None on file
Half-life as stated on file: Subcutaneous; interval not disclosed
No amino acid sequence is on file for SRK-439, so none is drawn rather than guessed from a name.
The studies we cite
- Review of studies2026Scholar Rock first quarter 2026 results and pipeline update
This is a company update, not a study. It says first results from the early study of SRK-439 in people are expected in the second half of 2026.
Phase 1 topline for SRK-439 guided to H2 2026.
- Animal study2025New SRK-439 preclinical data
In primates, lean mass went up. In mice, fat came back less after a GLP-1 drug was stopped.
Lean-mass gains in primates; reduced fat rebound after GLP-1 withdrawal in mice.
Common questions
Has SRK-439 been tested in people?
Not in any study cited here. SRK-439 is Scholar Rock's follow-up to apitegromab, built to be self-injected alongside GLP-1 drugs. First results in people are expected in the second half of 2026.
What is the SRK-439 dosage?
No human dose established. No published study on this page has given this compound to people and reported a result. 1 animal study, no human study
Is SRK-439 FDA-approved?
Investigational; in early safety studies
How is SRK-439 different from apitegromab?
Same target. SRK-439 is built as a shot people give themselves, for obesity. Apitegromab is given through a drip, for spinal muscular atrophy.