Here's an interesting problem: What if your biggest competitive threat shows up before you even get to market? That's the dilemma facing Structure Therapeutics Inc. (GPCR), which is still months away from seeking approval for its experimental weight-loss pill but already bracing for an obstacle that has haunted the entire obesity drug sector.

The culprit? Compounded copycat versions that have flooded the market and refuse to go away.

Structure is advancing an oral small molecule called aleniglipron, which resembles Eli Lilly and Co.'s (LLY) orforglipron but features a shorter half-life. The company shared promising topline data in December 2025 from its ACCESS clinical program, including results from the core Phase 2b ACCESS study, the exploratory ACCESS II study, and interim data from ongoing body composition and open-label extension studies.

The Clinical Results Look Solid

In the core Phase 2b ACCESS study, aleniglipron delivered a clinically meaningful and statistically significant placebo-adjusted mean weight loss of 11.3% at the 120 mg dose at 36 weeks. The treatment saw a 10.4% adverse event-related discontinuation rate across all active arms.

The exploratory ACCESS II study produced even more impressive numbers. Aleniglipron achieved placebo-adjusted mean weight loss of up to 15.3% with a 240 mg dose at 36 weeks. Structure is also running three additional clinical studies designed to competitively position aleniglipron and support the Phase 3 program design.

The company recently expanded its pipeline beyond aleniglipron. In December 2025, Structure initiated a first-in-human Phase 1 clinical study of ACCG-2671, its lead oral small molecule amylin receptor agonist for obesity.

But CEO Raymond Stevens Isn't Celebrating Yet

Despite the encouraging clinical data, Stevens warned at the JPMorgan Healthcare Conference on Wednesday that unapproved alternatives could undermine new entrants before they even reach patients.

"It's the thing I fear the most," Stevens said in an interview. "We've really got to get this compounding issue under control."

The compounding problem emerged when demand for branded obesity treatments massively outpaced supply. Patients turned to compounded versions out of necessity. The twist? Even though supply constraints have largely eased for established drugs, compounded alternatives have stuck around.

The Numbers Tell the Story

Novo Nordisk A/S' (NVO) CEO Mike Doustdar recently estimated that up to 1.5 million patients in the U.S. may still be using compounded weight-loss drugs. The reason is straightforward: they're cheaper than branded options.

Those lower-cost alternatives could seriously limit adoption of newly approved drugs and create pricing pressure across the entire sector. That's bad news for any company trying to break into this market, no matter how good their clinical data looks.

Does Structure Have Any Protection?

Stevens thinks Structure might have a fighting chance. Aleniglipron is a small-molecule drug, which typically requires a more complex manufacturing process than the peptide-based injectables currently dominating the market. Popular treatments like Lilly's Zepbound and Novo's Wegovy are peptides, which Stevens noted are generally easier to replicate in compounding pharmacies.

Still, that manufacturing complexity might not be enough of a moat. Drugmakers across the industry broadly agree that regulatory oversight has fallen short. Companies argue the U.S. Food and Drug Administration hasn't done nearly enough to curb the continued production and sale of compounded versions now that the original shortage crisis has ended.

It's a frustrating situation for companies that have invested hundreds of millions in clinical trials and regulatory approval processes, only to compete against alternatives that didn't go through the same rigorous vetting.

GPCR Price Action: Structure Therapeutics shares were down 0.80% at $83.65 at the time of publication on Thursday.