Prime Therapeutics claims data show real-world one-year persistence on tirzepatide around 65%

A new claims analysis from pharmacy benefit company Prime Therapeutics reports that the share of commercially insured US adults who stay on a high-potency, weight-loss GLP-1 drug for a full year has nearly doubled since 2021 — from 33.2% among people who started in 2021 to 60.9% among those who started in the first half of 2024 ^[1].

The study looked only at Wegovy (semaglutide) and Zepbound (tirzepatide), the two products approved for weight management, and only in people without diabetes ^[1]. Researchers used Prime's combined medical and pharmacy claims from an average monthly membership of 17.9 million commercially insured people ^[1].

What the study measured

Investigators identified 62,650 members without diabetes who newly started one of these drugs between January 1, 2021, and June 30, 2024. Of those, 33,607 — 53.6% — met the full study criteria, which required continuous insurance enrollment with no more than a 15-day total gap for the 365 days before and after the first fill, and no GLP-1 prescription in the prior year ^[1]. People with a diabetes diagnosis or diabetes drug claim before starting, and anyone under 19, were excluded ^[1]. The average age was 45.7 years and 75.5% were female ^[1].

"Persistence" here does not mean perfect use. It was defined as going no more than 60 days between the end of one prescription's days supply and the next fill during the year after starting ^[1]. Adherence was measured separately as a proportion of days covered of at least 80% ^[1]. Switching between GLP-1 products was allowed and did not count as stopping ^[1].

The numbers by drug and year

For semaglutide, 1-year persistence was 33.2% for 2021 starters, 34.1% in 2022, 39.8% in 2023, and 58.6% in the first half of 2024 ^[1].

For tirzepatide, which was only available in the later years studied, persistence was 64.0% for 2023 starters and 64.8% in the first half of 2024 ^[1].

The authors point to shortages easing as one likely reason persistence improved, noting that GLP-1 supply problems and changes in product availability since 2021 complicated access ^[1]. They also list other possible contributors: better dose escalation, better side-effect management, and weight-loss lifestyle programs ^[1].

An important caveat: the study did not measure why people stopped. The authors write that more research is needed to understand reasons for discontinuation and the long-term cost-effectiveness of these drugs ^[1]. The abstract also does not report the adherence results themselves, only the definition used ^[1]. And the four authors are employed by the study sponsor, Prime Therapeutics ^[1].

Why it matters for patients

Clinical trials of these medicines are run under tightly controlled conditions, with free drug and regular study visits. Real-world persistence has been substantially lower than trial numbers ^[1]. This analysis puts a figure on that gap and shows it narrowing, at least among people with commercial insurance.

The drug-to-drug difference is the part likely to draw attention. In 2023, roughly two-thirds of tirzepatide starters were still filling prescriptions a year later versus about four in ten semaglutide starters ^[1]. By the first half of 2024 the gap narrowed to 64.8% versus 58.6% ^[1]. Because this is a claims study and not a randomized comparison, it cannot separate the effect of the drug itself from supply availability during those specific periods, insurance coverage rules, or differences in who was prescribed what. Wegovy shortages and changes in product availability were happening across the study window ^[1].

The results also apply to a specific group: adults with commercial insurance who kept that coverage for two straight years and had no diabetes ^[1]. Nearly half of initiators — 46.4% — were dropped from the analysis for not meeting those criteria ^[1], which suggests people who switch jobs, lose coverage, or pay cash may look different. The study covers starters only through June 30, 2024, so it says nothing about 2025 or later starters, about newer options such as orforglipron (Foundayo), or about compounded versions.

What happens next

The study's own conclusion is that more work is needed on why people discontinue and on long-term cost-effectiveness ^[1]. Neither question is answered by this dataset, and no follow-up timeline is given in the published abstract ^[1].