The total sample for the study was 173 patients (Fig. 1). Approximately 24 months of follow-up data were collected from 94.0% of the patients, and the remaining 6.0% had between 12 and 24 months of available follow-up data.

Demographic and clinical characteristics

Patient mean (SD) age was 69.8 (7.4) years (Table 1). Mean (SD) body mass index (BMI) was 24.8 kg/m2 (5.1) and 43.4% had a BMI in the overweight (25.0 to 29.9 kg/m2) or obese (30.0 kg/m2 or higher) range. The most common chronic preexisting conditions were cardiovascular disease (50.3%), gastrointestinal conditions (32.4%), and endocrine disorders (24.9%).

Table 1 Patient characteristicsBaseline history of osteoporosis and treatment

Mean (SD) time since diagnosis of OP at the time of study enrollment was 96.2 (61.4) months. Just over half of patients (52.0%) were diagnosed through routine screening, 28.9% were diagnosed at the time of fracture, and 20% were diagnosed due to risk factors or OP symptoms. Patients could have multiple circumstances leading to OP diagnosis. Bone mineral density assessments by DXA were used to confirm a diagnosis of OP in 82.1%, and conventional x-ray confirmed the diagnosis in 12.1% of patients. Most patients (162/173 [93.6%]) had ≥ 1 DXA scans after initiation of treatment with abaloparatide. The median baseline T-scores were − 2.50, − 2.00, and − 2.85 for femoral neck, total hip, and lumbar spine, respectively.

Most patients (136/173 [78.6%]) had prior treatment for osteoporosis before abaloparatide and (45/136 [33.1%]) had previously been treated with an anabolic drug. The mean (SD) time between discontinuation of a prior OP medication and initiation of abaloparatide was 1.7 (3.2) years. Twenty-four percent (42/173) of patients changed treatment from teriparatide to abaloparatide, and the reasons for switching included a mandatory formulary switch (33.3%), financial/copay concerns (19.0%), tolerability issues with teriparatide (19.0%), lack of efficacy (9.5%), and hypercalcemia (4.8%). For the remaining patients, the reason for switching was unknown or not available.

Follow-up monitoring

In the 2-year follow-up period after beginning abaloparatide, 96.0% of patients visited with a healthcare professional for their osteoporosis, with a median of 3 visits. Over half (55.5%) received drug support for their osteoporosis medication. Of these, 26.0% were participants in a support program provided by Radius Health, Inc. Of 54 patients with OP fractures since diagnosis, 27.8% participated in a fracture liaison service program (FLS; a program to support patients in the weeks after a fracture has been surgically treated).

Central DXA scans were used most frequently (93.6%) to monitor patients; 8.1% used conventional x-ray; 7.5% assessed vertebral fractures by spine radiography or vertebral fracture analysis (VFA). Bone turnover markers (BTMs) were assessed in (70/173 [40.5%] patients) at some point following their diagnosis, with a median of 3 assessments. Of those evaluated with BTMs, 65 patients received at least one postbaseline BTM assessment, with 46 (65.7%) for P1CP or procollagen type 1 N-terminal propeptide (formation markers) and 26 (37.1%) for markers of resorption urinary or serum collagen type 1 cross-linked C-telopeptide.

Treatment patterns following abaloparatide treatment initiation

Over half of patients (84/158 [53.2%]) were treated with abaloparatide for ≥ 18 months (Table 2). The median duration of anabolic therapy for patients who completed treatment was 18.6 months. Mean (SD) duration of abaloparatide therapy was 17.2 (8.1) months and was longer for patients who were previously treated for OP (18.0 [8.2] months) compared to those without a history of OP treatment (14.6 [7.3] months). Median duration of cumulative exposure to anabolics, including patients who stopped and restarted therapy, was 22.5 months. Study sites were asked to indicate whether patients adhered to treatment (took medication as prescribed). About 5.6% of patients had a gap in therapy with a mean (SD) of 62.4 (90.5) days. The most common reasons for discontinuation of treatment were financial in nature (31.2%) and tolerability issues (22.8%) (Table 3).

Table 2 Treatment patterns following initiation of abaloparatideTable 3 Reason for discontinuation of treatment with abaloparatideTreatment after abaloparatide

Fifty-one percent (82/162) continued treatment with another OP medication after their course of abaloparatide within the 24-month follow-up period. Denosumab was the most common initial follow-on therapy (48.8%), followed by zoledronic acid (20.8%). The median time between the completion of treatment with abaloparatide and the beginning of the next therapy was 21 days with a maximum reported time between therapies of 12.3 months. Seventy-two of 82 (87.8%) patients were still on their initial follow-on OP therapy at the end of the study.

Additional treatment following abaloparatide

Fewer than 5% of patients received more than one treatment after abaloparatide and within 24 months of abaloparatide initiation, including alendronate or zoledronic acid. The median time from stopping the first follow-on OP drug after abaloparatide to the second OP drug (index to index) was 3 days. Of the seven patients who switched to a second drug, four (57.1%) did so due to tolerability with the first treatment that followed abaloparatide. For 5/7 (71.4%) patients who started a second follow-on treatment, that therapy was still ongoing at the end of the study period and was to be continued indefinitely if tolerated in 57.1%.

DXA results

Although DXA scan results were available for most patients during the follow-up period, only 48/173 (27.7%) patients (Table 4) had BMD results within the necessary time frames for inclusion in the baseline, 12 months, and 24 months analyses, as described in the methods. Median BMD T-scores increased from baseline (femoral neck, − 2.5; total hip, − 2.0; lumbar spine, − 2.9) compared with 12 months (femoral neck, − 2.4; total hip, − 1.9; lumbar spine, − 1.7) and 24 months (femoral neck, − 2.3; total hip, − 1.8; lumbar spine, − 1.7).

Table 4 Median BMD T-score changes following abaloparatide