Doctor PREDICTS Future Muscle Drugs: Bimagrumab, Follistatin, Orforglipron & More
A urologist's January 2026 update on muscle-building drugs: follistatin gene therapy, the bimagrumab and Regeneron antibody trials, and why he thinks pharma is deprioritizing them.
With Dr. Alex Tatem (board-certified urologist, fellowship-trained men's health specialist)
Key moments
Tap a moment to play the video from there.
- 0:00Why this follow-up videoTatem says the trials he previewed earlier have now finished, stalled or been terminated. He also says viewers keep asking him about follistatin gene therapy.
- 1:12Myostatin, activin and follistatin primerHe explains the three proteins as a growth brake, a broader regulator and the protein that holds both back. He warns that blocking activin body-wide could cause side effects.
- 2:32Why follistatin is hard to injectTatem gives two reasons: it blocks activin too aggressively, and its half-life is very short, so continuous infusion would be needed.
- 3:00Minicircle plasmid gene therapy explainedHe describes the plasmid approach, the company's claimed 18-month duration and its claimed antibiotic kill switch. He also notes it is not available in the United States.
- 4:34Brian Johnson's reported resultsTatem relays a reported 160% follistatin rise at four months and 7% more lean mass at six months. He cautions that many other variables changed.
- 5:32Bimagrumab with semaglutide trialHe covers the BELIEVE results, with 22.1% body weight loss of which 92.8% was fat. Tatem frames the drug as preventing muscle loss rather than adding muscle.
- 6:38Regeneron triplet trial problemsTatem says the semaglutide, trevogrumab and garetosmab triplet preserved muscle but caused high discontinuation, skin problems and bleeding events.
- 7:02Why pharma may shelve these drugsHe offers his own conjecture that cold-chain biologics are costly and secondary to GLP-1s, especially Lilly's oral orforglipron.
- 8:37Conclusion and takeawaysTatem calls the gene therapy interesting but underwhelming for its price and the antibodies promising but stuck. He says he will keep tracking the orforglipron trials.
What the video says
Dr. Alex Tatem, who describes himself as a board-certified urologist, follows up on an earlier video about myostatin inhibitors. He says the trials have now concluded, been suspended or collapsed, and asks whether muscle growth through drugs outside the androgenic pathway is dead or just complicated. The video is a commentary with a humorous tone, and he labels his later conclusions as conjecture.
He starts with a primer. According to Tatem, myostatin acts as a brake on muscle growth, activin does a similar job but also touches wound healing, inflammation and reproductive hormones, and follistatin binds both. He argues that injecting follistatin directly is impractical because it blocks activin too broadly and has a very short half-life. He then describes a plasmid gene therapy offered by a company called Minicircle at a clinic in Honduras, which he says is priced at 25 grand and is not allowed in the United States. Minicircle claims the effect lasts about 18 months and that a doxycycline-triggered kill switch exists. Tatem relays Brian Johnson's reported figures, a 160% rise in follistatin at four months and 7% more lean mass at six months, and notes that Johnson changed many other things at the same time. He says human follistatin data show a minor effect compared with preclinical studies.
On the pharma side, Tatem summarizes the BELIEVE trial of bimagrumab plus semaglutide presented at the ADA sessions in June 2025. The combination group lost 22.1% of body weight, and he says 92.8% of that was fat, against roughly 70 to 75% fat with semaglutide alone. He says Lilly terminated a phase 2b trial of the combination in September 2025 for strategic business reasons. He also reports that Regeneron's COURAGE trial of a triplet with semaglutide, trevogrumab and garetosmab preserved muscle but brought high discontinuation, skin problems and bleeding events.
His closing view is that Lilly is prioritizing orforglipron, an oral GLP-1 pill, because it is easier to manufacture and ship than cold-chain biologics. He concludes that the human data for gene therapy are underwhelming for the price and that the antibodies look useful for muscle preservation but are stalled.
On each compound
Follistatin-3441:30
Tatem describes follistatin as the natural binder of myostatin and activin. He says direct injection is impractical because of its broad activin blocking and short half-life, and that human data show a minor effect compared with preclinical studies.
See how your DNA reads Follistatin-344Bimagrumab5:36
Tatem says Lilly's bimagrumab, paired with semaglutide in the BELIEVE trial, gave 22.1% body weight loss with 92.8% of it fat. He adds that Lilly terminated a phase 2b trial of the combination in September 2025 for strategic business reasons.
See how your DNA reads BimagrumabSemaglutide5:36
According to Tatem, weight loss on semaglutide alone is only about 70 to 75% fat, with the rest being muscle. He presents it as the backbone drug the muscle-preserving antibodies are paired with.
See how your DNA reads SemaglutideWhat this video doesn’t settle
- The video relies on Brian Johnson's self-reported numbers, with no control group and many other changes happening during his protocol.
- Minicircle's claimed 18-month duration and antibiotic kill switch are company claims that Tatem relays but does not verify.
- Tatem's explanation for why Lilly ended the bimagrumab combination trial is his own conjecture, since the company only cited strategic business reasons.
Questions this video answers
Does follistatin gene therapy build muscle in humans?
Tatem says the human evidence is modest. He cites Brian Johnson's self-reported 7% lean mass gain at six months, notes that Johnson changed many other things, and says human results are minor compared with preclinical studies.
What happened to the bimagrumab and semaglutide combination trial?
Tatem says the BELIEVE results showed 22.1% body weight loss, with 92.8% of it fat. He also says Lilly terminated a phase 2b trial of the combination in September 2025, citing strategic business reasons.
Why is blocking activin considered risky?
Tatem says activin is found throughout the body and affects wound healing, inflammation and reproductive hormones. He mentions possible nosebleeds, healing problems and reproductive issues, and says Regeneron's triplet trial had skin problems and bleeding events.
What is Minicircle follistatin gene therapy and what does it cost?
Tatem describes it as a plasmid that carries instructions for making follistatin and does not integrate into the genome. He says Minicircle claims it lasts about 18 months and has an antibiotic kill switch, and that it costs 25 grand at a clinic in Honduras.
Why does Tatem think pharma is dropping muscle-preservation drugs?
In what he calls pure conjecture, Tatem says the antibodies are expensive cold-chain biologics. He argues Lilly is putting its resources into orforglipron, an oral GLP-1 pill that is easier to distribute.
Video by Dr. Alex Tatem on YouTube, embedded as published. The summary is written by PeptidesDNA from the video; every claim in it is the speaker’s. Not affiliated with or endorsed by the creator. Not medical advice.
