Gary Hattersley

IMPORTANCE: Additional therapies are needed for prevention of osteoporotic fractures. Abaloparatide is a selective activator of the parathyroid hormone type 1 receptor. OBJECTIVE: To determine the efficacy and safety of abaloparatide, 80 μg, vs placebo for prevention of new vertebral fracture in postmenopausal women at risk of osteoporotic fracture. DESIGN, SETTING, AND PARTICIPANTS: The Abaloparatide Comparator Trial In Vertebral Endpoints (ACTIVE) was a phase 3, double-blind, RCT (March 2011-October 2014) at 28 sites in 10 countries. Postmenopausal women with bone mineral density (BMD) T score ≤-2.5 and >-5.0 at the lumbar spine or femoral neck and radiological evidence ≥2 mild or ≥1 moderate lumbar or thoracic vertebral fracture or history of low-trauma nonvertebral fracture within the past 5 years were eligible. Postmenopausal women (>65 y) with fracture criteria and a T score ≤-2.0 and >-5.0 or without fracture criteria and a T score ≤-3.0 and >-5.0 could enroll. INTERVENTIONS: Blinded, daily subcutaneous injections of placebo (n = 821); abaloparatide, 80 μg (n = 824); or open-label teriparatide, 20 μg (n = 818) for 18 months. MAIN OUTCOMES AND MEASURES: Primary end point was percentage of participants with new vertebral fracture in the abaloparatide vs placebo groups. Sample size was set to detect a 4% difference (57% risk reduction) between treatment groups. Secondary end points included change in BMD at total hip, femoral neck, and lumbar spine in abaloparatide-treated vs placebo participants and time to first incident nonvertebral fracture. Hypercalcemia was a prespecified safety end point in abaloparatide-treated vs teriparatide participants. RESULTS: Among 2463 women (mean age, 69 years [range, 49-86]), 1901 completed the study. New morphometric vertebral fractures occurred less frequently in the active treatment groups vs placebo. The Kaplan-Meier estimated event rate for nonvertebral fracture was lower with abaloparatide vs placebo. BMD increases were greater with abaloparatide than placebo (all P < .001). Incidence of hypercalcemia was lower with abaloparatide (3.4%) vs teriparatide (6.4%) (risk difference [RD], −2.96 [95%CI, −5.12 to −0.87]; P = .006). [table: see text]. CONCLUSIONS AND RELEVANCE: Among postmenopausal women with osteoporosis, the use of subcutaneous abaloparatide, compared with placebo, reduced the risk of new vertebral and nonvertebral fractures over 18 months. Further research is needed to understand the clinical importance of RD, the risks and benefits of abaloparatide treatment, and the efficacy of abaloparatide vs other osteoporosis treatments. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01343004.

Little is known about the regulatory signals involved in tendon and ligament formation, and this lack of understanding has hindered attempts to develop biologically based therapies for tendon and ligament repair. Here we report that growth and differentiation factors (GDFs) 5, 6, and 7, members of the TGF-beta gene superfamily that are most related to the bone morphogenetic proteins, induce neotendon/ligament formation when implanted at ectopic sites in vivo. Analysis of tissue induced by GDF-5, 6, or 7, containing implants by currently available morphological and molecular criteria used to characterize tendon and ligament, adds further evidence to the idea that these GDFs act as signaling molecules during embryonic tendon/ligament formation. In addition, comparative in situ localizations of the GDF-5, 6, and 7 mRNAs suggest that these molecules are important regulatory components of synovial joint morphogenesis.

The PTH receptor type 1 (PTHR1) mediates the actions of two endogenous polypeptide ligands, PTH and PTHrP, and thereby plays key roles in bone biology. Based on its capacity to stimulate bone formation, the peptide fragment PTH (1-34) is currently in use as therapy for osteoporosis. Abaloparatide (ABL) is a novel synthetic analog of human PTHrP (1-34) that holds promise as a new osteoporosis therapy, as studies in animals suggest that it can stimulate bone formation with less of the accompanying bone resorption and hypercalcemic effects that can occur with PTH (1-34). Recent studies in vitro suggest that certain PTH or PTHrP ligand analogs can distinguish between two high-affinity PTHR1 conformations, R(0) and RG, and that efficient binding to R(0) results in prolonged signaling responses in cells and prolonged calcemic responses in animals, whereas selective binding to RG results in more transient responses. As intermittent PTH ligand action is known to favor the bone-formation response, whereas continuous ligand action favors the net bone-resorption/calcemic response, we hypothesized that ABL binds more selectively to the RG vs the R(0) PTHR1 conformation than does PTH (1-34), and thus induces more transient signaling responses in cells. We show that ABL indeed binds with greater selectivity to the RG conformation than does PTH (1-34), and as a result of this RG bias, ABL mediates more transient cAMP responses in PTHR1-expressing cells. The findings provide a plausible mechanism (ie, transient signaling via RG-selective binding) that can help account for the favorable anabolic effects that ABL has on bone.

CONTEXT: Abaloparatide is a novel synthetic peptide analog of parathyroid hormone-related protein (PTHrP) that is currently being developed as a potential anabolic agent in the treatment of postmenopausal osteoporosis. OBJECTIVE: This study sought to assess the effects of abaloparatide on bone mineral density (BMD) at the lumbar spine, total hip, and femoral neck in postmenopausal women with osteoporosis. DESIGN: Multi-center, multi-national, double-blind placebo controlled trial in which postmenopausal women were randomly assigned to receive 24 weeks of treatment with daily sc injections of placebo, abaloparatide, 20, 40, or 80 μg, or teriparatide, 20 μg. A 24-week extension was also performed in a subset of subjects. PARTICIPANTS: Postmenopausal women with osteoporosis (n = 222). MAIN OUTCOME MEASURES: BMD by dual-x-ray absorptiometry and biochemical markers of bone turnover. RESULTS: At 24 weeks, lumbar spine BMD increased by 2.9, 5.2, and 6.7% in the abaloparatide, 20-, 40-, and 80-μg groups, respectively, and 5.5% in the teriparatide group. The increases in the 40- and 80-μg abaloparatide groups and the teriparatide group were significantly greater than placebo (1.6%). Femoral neck BMD increased by 2.7, 2.2, and 3.1% in abaloparatide, 20-, 40-, and 80-μg groups, respectively, and 1.1% in the teriparatide group. The increase in femoral neck BMD with abaloparatide, 80 μg was significantly greater than placebo (0.8%). Total hip BMD increased by 1.4, 2.0, and 2.6% in the abaloparatide, 20-, 40-, and 80-μg groups, respectively. The total hip increases in the 40- and 80-μg abaloparatide groups were greater than both placebo (0.4%) and teriparatide (0.5%). CONCLUSIONS: Compared with placebo, 24 weeks of daily sc abaloparatide increases BMD of the lumbar spine, femoral neck, and total hip in a dose-dependent fashion. Moreover, the abaloparatide-induced BMD increases at the total hip are greater than with the marketed dose of teriparatide. These results support the further investigation of abaloparatide as an anabolic therapy in postmenopausal osteoporosis.

The localized expression of a number of extracellular matrix genes was evaluated over time in a novel rat rotator cuff injury model. The supraspinatus tendons of rats were severed at the bony insertion and repaired surgically. The healing response was evaluated at 1, 2, 4, and 8 weeks post-injury using histologic and in situ hybridization techniques. Expression patterns of collagens (I, II, III, IX, X, XII), proteoglycans (decorin, aggrecan, versican, biglycan, fibromodulin), and other extracellular matrix proteins (elastin, osteocalcin, alkaline phosphatase) were evaluated at the healing tendon to bone insertion site. Histologic results indicate a poor healing response to the injury, with only partial recreation of the insertion site by 8 weeks. In situ hybridization results indicate a specific pattern of genes expressed in each zone of the insertion site (i.e., tendon, fibrocartilage, mineralized cartilage, bone). Overall, expression of collagen types I and XII, aggrecan, and biglycan was increased, while expression of collagen type X and decorin was decreased. Expression of collagen type I, collagen type XII, and biglycan decreased over time, but remained above normal at 8 weeks. Results indicate that the rat supraspinatus tendon is ineffective in recreating the original insertion site, even at 8 weeks post-injury, in the absence of biological or biomechanical enhancements.