Abstract
BACKGROUND:
Glucagon-like peptide-1 (GLP-1) receptor agonists, including a dual GLP-1/glucose-dependent insulinotropic polypeptide (GIP) agonist, have expanded treatment options for overweight and obesity. However, real-world data within Medicaid populations remain limited.
OBJECTIVE:
To assess 6-month persistence, adherence, and effectiveness of GLP-1 and GLP-1/GIP therapies among Massachusetts Medicaid (MassHealth) members.
METHODS:
This retrospective, claims-based analysis identified continuously enrolled MassHealth adults, with or without diabetes, initiating GLP-1 or GLP-1/GIP treatment with semaglutide (Wegovy) or tirzepatide (Zepbound) between July 1, 2024, and December 31, 2024. The co–primary outcomes were persistence, defined as no more than 56 days between fills, and adherence, defined as proportion of days covered (PDC) of at least 80%. A key secondary outcome examined the rate at which a subgroup of members achieved at least a 5% reduction in body weight from baseline as documented on prior authorization (PA) recertification at 6 months.
RESULTS:
Among 7,493 members, rates of persistence and adherence to treatment were 60.8% and 60.1%, respectively. Member-specific factors associated with lower rates of persistence and adherence included male sex, age (<40 years), diabetes, and a lack of weight-related comorbidities. Among a subgroup of members on tirzepatide, semaglutide, or with exposure to both, 86.5% of members had at least a 5% reduction in body weight from baseline at 6 months.
CONCLUSIONS:
At 6 months, MassHealth members showed moderate persistence and adherence to GLP-1 or GLP-1/GIP treatment. Tirzepatide and semaglutide were effective in producing significant weight loss at 6 months among a subgroup of highly persistent and adherent members.
Plain language summary
This study looked at Massachusetts Medicaid members who began treatment with semaglutide or tirzepatide for weight loss. After 6 months, approximately 61% of members stayed on treatment and 60% took it as prescribed. In a smaller group, 86.5% of members lost at least 5% of their starting weight after 6 months. These results show that both drugs may help many patients lose weight when used regularly.
Implications for managed care pharmacy
This analysis found that 6-month persistence (60.8%) and adherence (60.1%) to semaglutide or tirzepatide for overweight or obesity were lower than clinical trial benchmarks. However, real-world effectiveness was high among members who remained on therapy and took it as prescribed. These findings underscore the importance of identifying barriers to sustained use, particularly in Medicaid populations, as payers assess the value of these treatments and advance equitable approaches to obesity care.
Overweight and obesity are multisystem chronic diseases with increasing prevalence, representing a significant public health concern. Body mass index (BMI), although an imperfect measure of adiposity, is used to define overweight (BMI 25-29.9 kg/m2) and obesity (BMI ≥ 30 kg/m2).1 In 2023, the Behavioral Risk Factor Surveillance System reported that 27.4% of Massachusetts adults were obese and 35.2% were overweight, relative to the national averages of 34.3% and 34.4%, respectively.2
Obesity is a major contributor to morbidity and mortality because of its association with the development and exacerbation of comorbidities, including diabetes, obstructive sleep apnea (OSA), cardiovascular disease (CVD), nonalcoholic steatohepatitis (NASH), and certain cancers.3 Although challenging to quantify, the annual obesity-related medical costs in the United States were estimated to be approximately $173 billion in 2019.4
Consensus guidelines recommend initial management with dietary and lifestyle modifications. Pharmacotherapy is recommended as adjunctive treatment for those with an inadequate response to lifestyle interventions and a BMI of at least 30 kg/m2 or a BMI of at least 27 kg/m2 with 1 or more weight-related comorbidities. Weight loss of at least 5% from baseline within 6 months is generally considered clinically significant; however, weight loss of at least 10% may be necessary to see symptomatic improvement in those with certain weight-related comorbidities.5–7
Approval of glucagon-like peptide-1 (GLP-1) and GLP-1/glucose-dependent insulinotropic polypeptide (GIP) products significantly advanced the pharmacologic treatment of overweight and obesity, in some cases providing weight loss previously achievable only via bariatric surgery.8 Notable approvals include liraglutide (Saxenda, 2014), semaglutide (Wegovy, 2021), and the dual GLP-1/GIP receptor agonist tirzepatide (Zepbound, 2023).9 Off-label use of medications approved by the US Food and Drug Administration for the treatment of diabetes also occurs.
Members taking GLP-1 and GLP-1/GIP agonists in phase 3 clinical trials have consistently demonstrated high rates of adherence and persistence.10,11 However, available real-world adherence and persistence among commercially insured members are substantially lower, potentially limiting the cost-effectiveness of these agents.12 As payers weigh the value of covering these medications, more data are needed to quantify the rates at which members persist and adhere to therapy and the extent to which these medications result in clinically significant weight loss in real-world settings.
Given that overweight and obesity disproportionately affect low-income patients, Medicaid coverage of these agents has been proposed as a potential mechanism to reduce health disparities.13 Although Medicaid programs must cover these medications to treat diabetes, coverage for the treatment of overweight and obesity remains optional.14
MassHealth began covering GLP-1 and GLP-1/GIP medications for the treatment of overweight and obesity in January 2024. At that time, semaglutide (Wegovy) and liraglutide (Saxenda) were designated as preferred agents, whereas tirzepatide (Zepbound) was nonpreferred and required a trial with semaglutide or liraglutide before approval. On October 1, 2024, tirzepatide became a preferred agent no longer requiring a trial of semaglutide or liraglutide. On January 1, 2025, tirzepatide became the sole preferred GLP-1 for obesity or overweight, and semaglutide and liraglutide became noncovered agents for the treatment of overweight and obesity in adults.
The purpose of this analysis was to evaluate the real-world persistence and adherence to GLP-1 and GLP-1/GIP medications for overweight and obesity in the MassHealth population. A subgroup analysis of the MassHealth Fee for Service (FFS), Primary Care Clinician (PCC), and Primary Care Accountable Care Organization (PCACO) plans assessed the real-world effectiveness of GLP-1 and GLP-1/GIP medications measured as percent of body weight lost from baseline, as documented on prior authorization (PA) recertifications.
Methods
MassHealth medical claims, pharmacy claims, and enrollment data from January 1, 2024, to June 30, 2025, were collected for this analysis. SAS Studio Enterprise Edition (v3.81) was used for data collection; Microsoft Excel (version 2507) was used for data analysis. Data obtained included medical claims (eg, date of service and diagnoses), pharmacy claims (eg, fill dates, days supply, and generic sequence numbers), and eligibility information (eg, member demographics and enrollment information). As a noninterventional retrospective analysis of claims data, the institutional review board assigned a determination of not human research. Data were deidentified and Health Insurance Portability and Accountability Act compliant. This retrospective analysis followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline.15
This retrospective evaluation identified MassHealth members, with or without diabetes, newly initiated on GLP-1 or GLP-1/GIP treatment between July 1, 2024, and December 31, 2024 (index period), with either semaglutide or tirzepatide. Liraglutide was excluded because of low utilization limiting reporting because of the Centers for Medicare & Medicaid Services Cell Size Suppression Policy.16 The date of the first paid GLP-1 or GLP-1/GIP pharmacy claim in the index period was labeled the index date, with the first GLP-1 or GLP-1/GIP medication paid pharmacy claim labeled the index medication (Supplementary Figure 1 (219.3KB, pdf) , avaliable in online article).
Members aged at least 18 years on their index date, without claims for a GLP-1 or GLP-1/GIP medications (ie, tirzepatide, semaglutide, liraglutide, or dulaglutide) between January 1, 2024, and June 30, 2024, were included. Members with third-party liability (TPL) insurance or a gap in coverage, defined as at least 30 days between January 1, 2024, and June 30, 2025, were excluded (Figures 1 and 2). MassHealth coverage was defined as enrollment in FFS, PCC, PCACO, Managed Care Organization (MCO), or Accountable Care Partnership Plans (ACPP).
FIGURE 1.
Study Design Diagram
GLP-1 = glucagon-like peptide-1.
FIGURE 2.
Patient Attrition Diagram
FFS = Fee for Service; GIP = glucose-dependent insulinotropic polypeptide; GLP-1 = glucagon-like peptide-1; PA = prior authorization; PCACO = Primary Care Accountable Care Organization; PCC = Primary Care Clinician; TPL = third-party liability.
The primary outcomes of 6-month persistence and adherence were reported at the member-level by index GLP-1 medication. Switching between commonly used GLP-1 or GLP-1/GIP agents (ie, tirzepatide, semaglutide, liraglutide, or dulaglutide) was permitted. Persistence was defined as no more than 56 days between fills. MassHealth limits dispensing of GLP-1 and GLP-1/GIP medications to a 1-month supply at a time. Members were considered nonpersistent if they had a gap in therapy of more than 56 days (ie, one missed 28-day fill) during the 6-month follow-up period. Adherence was calculated using the proportion of days covered (PDC) method endorsed by the Pharmacy Quality Alliance (PQA) with 4 key exceptions: (1) all members were naive to GLP-1 or GLP-1/GIP treatment with no paid claims within the prior 180 days, (2) members with a single GLP-1 or GLP-1/GIP claim were included in the adherence measurement, (3) all members were continuously enrolled, and (4) patients on hospice, with end-stage renal disease, and those with at least 1 paid claim for insulin during the assessment period were included in this analysis.17 These modifications to the PQA-endorsed measure of adherence were applied to ensure only inclusion of new GLP-1 or GLP-1/GIP initiators and to increase sample size. Members with a PDC of at least 80% were considered adherent. Sensitivity analyses explored how differing definitions of persistence and adherence impacted outcomes (Supplementary Tables 1 and 2 (219.3KB, pdf) ).
Secondary outcomes included 6-month effectiveness and the impact of weight-related comorbidities on persistence and adherence. Real-world effectiveness of GLP-1 and GLP-1/GIP medications was measured for members enrolled in MassHealth FFS/PCC/PCACO plans, for which data were available to study investigators. Effectiveness was defined as at least 5% reduction in weight from baseline weight (dated within 90 days of initial PA submission) to weight documented on first PA recertification for members enrolled specifically in MassHealth FFS/PCC/PCACO plans, for which data were available to study investigators. Data for this portion of the analysis were collected and maintained via an internal GLP-1 PA tracking system in Microsoft Excel by pharmacy personnel (Figure 2).
Weight-related comorbidities were identified using member-level data, medical claims data, and International Classification of Disease, Tenth Edition codes collected between January 1, 2024, and the member’s index date (Supplementary Figures 2 and 3, Table 4 (219.3KB, pdf) ). Key weight-related comorbidities included mental health (anxiety or depression), hypertension, dyslipidemia, asthma or chronic obstructive pulmonary disease, gastrointestinal reflux disease, OSA, osteoarthritis of the hip or knee, ischemic heart disease, polycystic ovary syndrome, CVD, and NASH.
Descriptive statistics compared covariates of interest, including member demographic (ie, age and sex) and clinical characteristics (ie, weight-related comorbidities) across index medications and for the entire study cohort (Supplementary Table 5 (219.3KB, pdf) ). Chi-square tests were used to evaluate differences in demographic and clinical characteristics across index GLP-1 medications. Among members who filled the same index medication, chi-square tests were used to evaluate the impact of demographic and clinical characteristics on persistence and adherence.
Results
A total of 7,493 MassHealth adults newly initiating GLP-1 or GLP-1/GIP therapy for overweight or obesity between July 1, 2024, and December 31, 2025, met the requisite inclusion and exclusion criteria requirements (Figure 2). Semaglutide was the most used index medication (70.5%), followed by tirzepatide (29.5%). The study population had a mean (±SD) age of 40.7 (±11.6) years and an average of 1.6 (±1.4) weight-related comorbidities, with women comprising most of the population (81.7%) (Table 1). Approximately 8.4% of members had a diagnosis of diabetes, which did not differ significantly by index medication (P = 0.2492). The prevalence of individual weight-related comorbidities was similar across index medications, except for NASH, which was more common in members with an index fill for tirzepatide compared with semaglutide (0.9% vs 0.5%, respectively, P = 0.0374; Supplementary Table 3 (219.3KB, pdf) ).
TABLE 1.
Demographics, Clinical Characteristics, and Outcomes by Index Medication
| All members,a N = 7,493 (100%) | Tirzepatide, n = 2,212 (29.5%) | Semaglutide, n = 5,281 (70.5%) | P valueb | |
|---|---|---|---|---|
| Demographicsc | ||||
| Female, n (%) | 6,124 (81.7) | 1,805 (81.6) | 4,319 (81.8) | 0.8514 |
| Male, n (%) | 1,369 (18.3) | 407 (18.4) | 962 (18.2) | |
| Age, mean (SD), years | 40.7 (11.6) | 40.3 (11.4) | 40.9 (11.6) | NR |
| Clinical characteristicsd | ||||
| Diabetes, n (%) | 628 (8.4) | 198 (9.0) | 430 (8.1) | 0.2492 |
| Number of weight-related comorbidities, mean (SD) | 1.6 (1.4) | 1.6 (1.4) | 1.6 (1.4) | N/A |
| GLP-1 or GLP-1/GIP outcomee | ||||
| Members persistent at 6 months without a 56-day gap between claims, n (%) | 4,555 (60.8) | 1,572 (71.1) | 2,983 (56.5) | <0.0001 |
| Members adherent at 6 months (PDC ≥ 80%), n (%) | 4,501 (60.1) | 1,547 (69.9) | 2,954 (55.9) | <0.0001 |
| Adherence (PDC), mean (SD) | 77.6 (26.6) | 82.7 (24.6) | 75.5 (27.1) | NR |
| Medication switches, n (%)f | ||||
| Members without switches | 3,785 (50.5) | 2,181 (98.6) | 1,604 (30.4) | <0.0001 |
| Members with ≥1 switch | 3,708 (49.5) | 31 (1.4) | 3,677 (69.6) | |
Bolded P values denote statistical signifigance (P<0.05).
Adult Medicaid members newly initiated on a GLP-1 or GLP-1/GIP medication for the treatment of overweight or obesity between July 1, 2024, and December 31, 2024.
P values for categorical variables are derived from a chi-square test.
Demographics data collected on date of index fill.
Clinical characteristics measured between January 1, 2024, and each member’s index date.
Measured for 180-day post-index date.
Count of member-level medication switches in the 180-day period post-index date.
GIP = glucose-dependent insulinotropic polypeptide; GLP-1 = glucagon-like peptide-1; N/A = not applicable; NR = not reported; PDC = proportion of days covered.
The primary study outcomes of GLP-1 and GLP-1/GIP persistence and adherence at 6 months were 60.8% and 60.1%, respectively, for the full study population. Members with an index fill for tirzepatide were significantly more likely compared with semaglutide to be persistent (71.7% vs 56.5%, P < 0.0001) and adherent (69.9% vs 55.9%, P < 0.0001) to GLP-1 therapy at 6 months.
Several demographic and clinical covariates were associated with differences in persistence and adherence at 6 months (Table 2). Women were more likely to be persistent (61.7% vs 56.8%; P = 0.0007) or adherent (60.7% vs 57.3%, P = 0.0192) to therapy at 6 months. Members younger than age 40 years were less likely, compared with members aged at least 40 years, to be persistent (58.9% vs 62.6%, P = 0.001) or adherent (57.6 vs 62.5%, P < 0.001) to treatment at 6 months. Members without weight-related comorbidities were less likely, compared with members with 1 or more weight-related comorbidities, to be persistent (58.0% vs 61.8%, P = 0.0038) or adherent (55.9% vs 61.5%, P < 0.0001) to GLP-1 or GLP-1/GIP treatment at 6 months. A diagnosis of diabetes was associated with lower persistence to treatment at 6 months (55.4% vs 61.3%, P = 0.0039) but did not significantly impact adherence (P = 0.1423).
TABLE 2.
Impact of Demographic and Clinical Covariates on Persistence and Adherence
| Demographic characteristics | |||
|---|---|---|---|
| Sex | Female (n = 6,124) | Male (n = 1,369) | P valuea |
| Members persistent at 6 months without a 56-day gap between claims, n (%) | 3,778 (61.7) | 777 (56.8) | 0.0007 |
| Members adherent at 6 months (PDC ≥ 80%), n (%) | 3,717 (60.7) | 784 (57.3) | 0.0192 |
| Age on index date | <40 y (n = 3,724) | ≥40 y (n = 3,769) | P valuea |
| Members persistent at 6 months without a 56-day gap between claims, n (%) | 2,194 (58.9) | 2,361 (62.6) | 0.001 |
| Members adherent at 6 months (PDC ≥ 80%), n (%) | 2,147 (57.6) | 2,354 (62.5) | <0.001 |
| Clinical characteristics | |||
| Diagnosis of diabetes | No diabetes (n = 6,865) | Diabetes (n = 628) | P valuea |
| Members persistent at 6 months without a 56-day gap between claims, n (%) | 4,207 (61.3) | 348 (55.4) | 0.0039 |
| Members adherent at 6 months (PDC ≥ 80%), n (%) | 4,141 (60.3) | 360 (57.3) | 0.1423 |
| Presence of weight-related comorbiditiesb | Zero weight-related comorbiditiesb (n = 1,952) | ≥1 weight-related comorbidityb (n = 5,541) | P valuea |
| Members persistent at 6 months without a 56-day gap between claims, n (%) | 1,133 (58.0) | 3,422 (61.8) | 0.0038 |
| Members adherent at 6 months (PDC ≥ 80%), n (%) | 1,092 (55.9) | 3,409 (61.5) | <0.0001 |
Bolded P-values denote statistical signifigance (P<0.05).
P values for categorical variables were derived from a chi-square test.
Weight-related comorbidities were defined as the presence of an International Classification of Diseases, Tenth Revision code in any of the first 9 diagnostic positions from January 1, 2024, to index date.
PDC = proportion of days covered.
Medication switching occurred in approximately half of the study population, with higher switch rates observed in members with a semaglutide index fill (69.6%) relative to tirzepatide (1.4%) (Table 3). Of members with a semaglutide index fill and at least 1 switch, the majority switched to tirzepatide (99.1%). Of the members with a tirzepatide index fill and at least 1 switch, approximately half switched to semaglutide (48.4%).
TABLE 3.
Characteristics, Persistence, Adherence, and Effectiveness of GLP-1 and GLP-1/GIP Medications in the Fee for Service/Primary Care Clinician/Primary Care Accountable Care Organization Subgroup
| All membersa (N = 341) | Tirzepatide (n = 232) | Semaglutide (n = 23) | Semaglutide and tirzepatideb (n = 86) | ||
|---|---|---|---|---|---|
| Baseline BMI, mean (SD) | 40.2 (8.6) | 40.6 (8.8) | 39.8 (8.3) | 39.2 (7.9) | |
| Time between baseline and recertification weight measurement, mean (SD), days | 166.3 (25.0) | 166.1 (23.8) | 157.7 (28.4) | 169.2 (26.5) | |
| Percent of total body weight lost at PA recertification, mean (SD) | 10.9 (6.8) | 11.4 (7.1) | 8.1 (6.6) | 10.4 (5.7) | |
| Members who lost ≥5% of body weight at PA recertification, n (%) | All members | 295 (86.5) | 204 (87.9) | 16 (70.0) | 75 (87.2) |
| Male | 40 (70.2) | NR | NR | NR | |
| Female | 255 (90.0) | NR | NR | NR | |
| Members persistent at 6 months without a 56-day gap between claims, n (%) | 298 (87.4) | 209 (90.1) | 13 (56.5) | 76 (88.4) | |
| Members adherent at 6 months (PDC ≥ 80%), n (%) | 310 (91.0) | 215 (92.7) | 15 (65.2) | 80 (93.0) | |
Adult Medicaid members newly initiated on a GLP-1 or GLP-1/GIP medication for the treatment of overweight or obesity between July 1, 2024, and December 31, 2024, with a PA recertification request with a weight documented at least 140 to no more than 220 days after baseline weight was measured.
Members with exposure to both semaglutide (Wegovy) and tirzepatide (Zepbound) but no other GLP-1 medications during study period.
BMI = body mass index; GIP = glucose-dependent insulinotropic polypeptide; GLP-1 = glucagon-like peptide-1; NR = not reported; PA = prior authorization; PDC = proportion of days covered.
The real-world effectiveness outcome was evaluated in a total of 341 FFS/PCC/PCACO members requesting PA recertification at approximately 6 months (Figure 2), representing less than 5% of the full study population. These members primarily had exposure to tirzepatide (68.0%), tirzepatide and semaglutide (25.2%), or semaglutide (6.7%). In total, approximately 86.5% of members lost at least 5% of their body weight at the time of PA recertification (Table 3). The average time between measurement of baseline weight and the weight submitted for PA recertification was 166 days, or approximately 5.5 months. Rates of 6-month persistence (87.4%) and adherence (91.0%) were high relative to the full study population. More women achieved at least 5% weight loss at time of recertification compared with men (90.0% vs 70.2%).
Discussion
This real-world study of MassHealth adults newly initiated on semaglutide or tirzepatide for the treatment of overweight or obesity found moderate rates of persistence (60.8%) and adherence (60.1%) to GLP-1 and GLP-1/GIP medications at 6 months. The persistence sensitivity analysis illustrated differences with the most lenient persistence definition of no more than 112 days between claims resulting in 84.0% of members being persistent at 6 months (Supplementary Table 1 (219.3KB, pdf) ). A sensitivity analysis of adherence showed minimal differences when comparing adherence among members with at least 1 fill relative to members with at least 2 fills (60.1% vs 64.5%; Supplementary Table 2 (219.3KB, pdf) ).
In comparison with these findings, a study of commercially insured obese adults without diabetes who newly initiated GLP-1 weight loss treatment in 2021 found that only 32.3% were persistent (defined as a ≤60-day gap), and 27.2% were adherent (PDC ≥ 80%) to therapy at 1 year, although shortages likely influenced these results.12 An updated analysis demonstrated members initiating treatment in the first quarter of 2024 had a 1-year persistence rate of 62.6%, with similar rates of 1-year persistence across semaglutide (62.7%) and tirzepatide (62.6%) products.18 Given that the current analysis used a stricter definition of persistence (≤56 days between fills) and measured persistence at 6 months, it is challenging to ascertain if members with Medicaid coverage and overweight or obesity are truly less persistent to GLP-1 or GLP-1/GIP treatment relative to commercially insured members. Barriers to medication access more prevalent in Medicaid populations may exist, including lack of transportation, language barriers, and lower health literacy, which may influence persistence and adherence to treatments for overweight and obesity.
Despite any existing barriers, the 6-month persistence rate of 60.8% observed in this evaluation is still lower than the 1-year persistence rate of at least 85% reported in many GLP-1 and GLP-1/GIP weight loss clinical trials.10,11 This finding raises important questions, as the health benefits of these treatments largely depend on sustained weight loss, which helps mitigate obesity-related complications such as hypertension, CVD, and OSA. However, these benefits may not be realized if the medications are discontinued prematurely or if clinically significant weight loss is not achieved or maintained.
Although this analysis found that members who first filled tirzepatide had significantly higher rates of persistence and adherence compared with members who first filled semaglutide, these results must be interpreted with caution given changes in preferred drug status occurring during the study period. On January 1, 2025, MassHealth switched to a sole preferred agent (tirzepatide) for overweight and obesity, meaning adult members taking semaglutide for overweight or obesity were required to switch to tirzepatide. MassHealth took several steps to proactively mitigate member disruption, including inputting PA approvals for tirzepatide for members with existing semaglutide PAs extending into 2025. Additionally, MassHealth completed targeted outreach to members and providers to inform them of the change. However, despite these efforts, it is possible that the change in preferred drug status may contribute to the lower persistence and adherence observed in members with an index claim for semaglutide in this analysis. Further research is required to elucidate differences in real-world persistence and adherence between GLP-1 and GLP-1/GIP therapies, particularly as novel agents enter the market.
In addition to product-specific differences in persistence and adherence, several member-specific covariates were associated with lower rates of persistence and adherence, including male sex, age (<40 years), a diagnosis of diabetes, and a lack of weight-related comorbidities. These results strengthen findings from prior research suggesting that younger patients who initiate treatment for overweight or obesity may be less likely to be persistent on GLP-1 medications.19 Additionally, these findings add to a growing body of literature suggesting men may be less likely to continue taking GLP-1 or GLP-1/GIP therapy for obesity of overweight relative to women.20 Tied with early data suggesting GLP-1 and GLP-1/GIP medications may be less effective in reducing body weight for men compared with women, these findings highlight an important area of further research.21,22
Product switching occurred among approximately half of the members included in this analysis, although changes in preferred drug status are presumably responsible for the high switch rates (69.6%) observed among members with an index fill for semaglutide. In comparison, a study of commercially insured adults with obesity and without diabetes who newly initiated GLP-1 weight loss treatment in 2021 found that just 14.8% of members with a semaglutide index fill switched to at least 1 other GLP-1 at 1 year.12 Although only 1.4% of members who started on tirzepatide switched medications within 6 months, nearly half of those who did switched to semaglutide. Although improved tolerability and effectiveness are often cited as reasons for switching from semaglutide to tirzepatide, the clinical rationale behind switching from tirzepatide to semaglutide is less understood; however, the presence of cardiovascular comorbidities and patient preference may influence this choice.23,24 Further research is warranted to better understand the growing role of social media and direct-to-consumer advertising on patient preferences when initiating or switching between GLP-1 or GLP-1/GIP treatments for overweight or obesity.
Although this analysis found that most FFS/PCC/PCACO MassHealth members (86.5%) taking a GLP-1 or GLP-1/GIP agent achieved at least 5% weight loss of their pretreatment body weight after approximately 6 months, this group represented less than 5% of the total study population. As such, findings may be biased toward members with greater engagement in care or more consistent contact with the health care system, limiting generalizability. Compared with the full study population (N = 7,493), members included in this effectiveness subgroup (n = 341) were highly persistent (87.4%) and adherent (91.0%) to treatment at 6 months, suggesting that effectiveness may be lower in the full study population. Nevertheless, these results suggest that, in a subgroup of highly persistent and adherent members, the observed effectiveness of GLP-1 and GLP-1/GIP medications appears consistent with clinical trial results.11,25–29 Although these medications appear highly efficacious for the treatment of overweight and obesity in a Medicaid population when taken as prescribed, further research is warranted to identify strategies to improve persistence and adherence in routine practice.
LIMITATIONS
This evaluation has several notable limitations. First, changes in preferred drug status on the MassHealth Drug List are a significant source of confounding and must be considered when interpreting data on persistence, adherence, medication switching, and the real-world effectiveness of semaglutide. Second, the analysis did not capture patients who paid out of pocket for compounded medications, although the extent of this is likely limited given that MassHealth covered these agents without cost-sharing during the study period. Third, selection bias likely influenced the evaluation of real-world effectiveness, as members who pursued PA recertification for continued GLP-1 or GLP-1/GIP therapy were more persistent and adherent and presumably experienced more weight loss relative to those who did not pursue PA recertification. In addition, recertification data were only accessible for members who remained in the FFS/PCC/PCACO population at the time of PA recertification, thus data from MCO/ACPP members were not available for this analysis. Medicaid redetermination did not impact cohort selection, as members disenrolled from MassHealth during the redetermination period (April 2023 to May 2024) would not have had a GLP-1 or GLP-1/GIP claim during the index period (July to December 2024) as required for study inclusion. Lastly, as this evaluation included data from a single state Medicaid program, the generalizability to Medicare, commercially insured populations, and other state Medicaid programs may be limited, particularly among states with differing rates of overweight and obesity. Although beyond the scope of this analysis, long-term data are needed to determine the real-world impact of these therapies on weight-related morbidity and mortality.
Conclusions
Overweight and obesity represent a significant public health threat in the United States. Although GLP-1 and GLP-1/GIP medications appear highly efficacious in a Medicaid population when taken as prescribed, this real-world study suggests persistence and adherence to these treatments is lower compared with reported findings from clinical trials. Understanding factors that impact the real-world persistence, adherence, and effectiveness of GLP-1 and GLP-1/GIP medications is essential as payers continue to evaluate the value of these medications and make informed formulary decisions.
Acknowledgments
The authors acknowledge Jeffrey Chan for his assistance in data collection.
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