Compounded retatrutide — will it be available before approval?

Happy to walk through the timeline. Here's my best estimate based on publicly available information and typical FDA review timelines:

Estimated Retatrutide Timeline

1. Phase 3 trials (TRIUMPH program): Currently enrolling/reading out. TRIUMPH-3 topline data reported. Additional readouts expected through mid-2026.
2. NDA/BLA filing: Eli Lilly has indicated they plan to submit to the FDA after sufficient Phase 3 data is available. Estimated filing: Q3-Q4 2026.
3. FDA review: Standard review is 10-12 months. Priority review (possible given the clinical significance) is 6-8 months. Estimated approval: Q2-Q4 2027.
4. Commercial launch: Typically 1-3 months after approval for manufacturing ramp-up. Estimated: H2 2027.
5. Insurance coverage: Varies by payor. Some may cover immediately; others may take 6-12 months to add to formulary. Widespread coverage: 2028.

Realistic answer: You might be able to get a prescription in late 2027 at the earliest, but getting insurance to cover it may take until 2028.

Caveats: Any clinical setback, manufacturing issue, or FDA request for additional data could push this out by 6-12+ months. These timelines are never guaranteed.

That timeline is reasonable but I'd note a few wildcards:

Accelerating factors:

• FDA has signaled willingness to prioritize obesity drugs given the public health crisis
• Lilly has significant experience with the FDA regulatory pathway from tirzepatide
• Manufacturing infrastructure for incretins is already being built out by Lilly (multiple new facilities)

Delaying factors:

• FDA may require cardiovascular outcomes data (CVOT) before approval, which takes longer
• Any unexpected safety signal in Phase 3 could require additional studies
• Manufacturing scale-up for a new biologic is complex — remember the tirzepatide supply constraints?

I think late 2027 is optimistic but possible. 2028 is more likely for most patients.

2027-2028?? That's so far away 😩 I was hoping it would be sooner. I guess I'll stay on tirzepatide in the meantime.

Follow-up question: would people on tirzepatide be able to switch to retatrutide easily? Or would you have to re-titrate from scratch? Having to go through the titration nausea again would be rough.

That's an excellent clinical question that honestly hasn't been studied yet. The TRIUMPH trials enrolled patients who were mostly GLP-1 naive (not previously on any GLP-1 RA). There may be sub-studies or post-marketing data on switching, but for now we don't have evidence-based guidance.

My educated guess: you would likely need to titrate retatrutide from the starting dose even if you're already on tirzepatide, because the glucagon receptor agonism component is new to your system. However, you might tolerate the GLP-1/GIP components better since you're already adapted to them.

This is exactly the kind of question your endocrinologist will need to navigate once the drug is approved. Switching protocols will likely emerge from clinical experience and post-marketing studies.