Sclerostin, a SOST protein secreted by osteocytes, negatively regulates formation of mineralized bone matrix and bone mass. We report the results of a randomized, double-blind, placebo-controlled multicenter phase 2 clinical trial of blosozumab, a humanized monoclonal antibody targeted against sclerostin, in postmenopausal women with low bone mineral density (BMD). Postmenopausal women with a lumbar spine T-score -2.0 to -3.5, inclusive, were randomized to subcutaneous blosozumab 180 mg every 4 weeks (Q4W), 180 mg every 2 weeks (Q2W), 270 mg Q2W, or matching placebo for 1 year, with calcium and vitamin D. Serial measurements of spine and hip BMD and biochemical markers of bone turnover were performed. Overall, 120 women were enrolled in the study (mean age 65.8 years, mean lumbar spine T-score -2.8). Blosozumab treatment resulted in statistically significant dose-related increases in spine, femoral neck, and total hip BMD as compared with placebo. In the highest dose group, BMD increases from baseline reached 17.7% at the spine, and 6.2% at the total hip. Biochemical markers of bone formation increased rapidly during blosozumab treatment, and trended toward pretreatment levels by study end. However, bone specific alkaline phosphatase remained higher than placebo at study end in the highest-dose group. CTx, a biochemical marker of bone resorption, decreased early in blosozumab treatment to a concentration less than that of the placebo group by 2 weeks, and remained reduced throughout blosozumab treatment. Mild injection site reactions were reported more frequently with blosozumab than placebo. In conclusion, treatment of postmenopausal women with an antibody targeted against sclerostin resulted in substantial increases in spine and hip BMD. These results support further study of blosozumab as a potential anabolic therapy for osteoporosis.

Two clinical studies were conducted to assess the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of single and multiple doses (intravenous [iv] and subcutaneous [sc]) of blosozumab in postmenopausal women, including prior/current bisphosphonate (BP) users. In these phase 1, randomized, subject-and investigator-blind, placebo-controlled studies, subjects received escalating doses of blosozumab: single iv doses up to 750 mg, single sc doses of 150 mg, multiple iv doses up to 750 mg every 2 weeks (Q2W) for 8 weeks, multiple sc doses up to 270 mg Q2W for 8 weeks, or placebo. Six subjects were randomized to each dose in the single-dose study (12 to placebo) and up to 12 subjects to each arm in the multiple-dose study. Blosozumab was well tolerated with no safety concerns identified after single or multiple administrations up to 750 mg. Dose-dependent responses were observed in sclerostin, N-terminal propeptide of procollagen type 1, bone-specific alkaline phosphatase, osteocalcin, C-terminal fragment of type 1 collagen, and bone mineral density (BMD) after single and multiple (up to 5) administrations of blosozumab. There was up to a 3.41% (p ¼ 0.002) and up to a 7.71% (p < 0.001) change from baseline in lumbar spine BMD at day 85 after single or multiple administrations of blosozumab, respectively. Prior BP use did not appear to have a clear impact on the effects of single doses of blosozumab when considering bone biomarker and BMD responses. Antibodies to blosozumab were detected by a screening assay, but no patterns with regard to dose or route of administration and no clear impact on blosozumab exposure or PD responses were identified. In summary, blosozumab was well tolerated and exhibited anabolic effects on bone. These findings support further investigation of blosozumab as a potential anabolic therapy for osteoporosis.

Abemaciclib, an inhibitor of cyclin dependent kinases 4 and 6, is indicated for metastatic breast cancer treatment. Reversible increases in serum creatinine levels of ~15–40% over baseline have been observed following abemaciclib dosing. This study assessed the in vitro and clinical inhibition of renal transporters by abemaciclib and its metabolites using metformin (a clinically relevant transporter substrate), in a clinical study that quantified glomerular filtration and iohexol clearance. In vitro , abemaciclib inhibited metformin uptake by organic cation transporter 2, multidrug and toxin extrusion (MATE)1, and MATE2‐K transporters with a half‐maximal inhibitory concentration of 0.4–3.8 μM. Clinically, abemaciclib significantly increased metformin exposure but did not significantly affect measured glomerular filtration rate, serum neutrophil gelatinase‐associated lipocalin (NGAL), serum cystatin‐C, or the urinary markers of kidney tubular injury, NGAL and kidney injury molecule‐1.

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Administration of blosozumab, a humanized monoclonal antibody that binds sclerostin, increases bone formation and bone mineral density (BMD) in postmenopausal women with low BMD. To evaluate the effect of discontinuing blosozumab, we studied women enrolled in a 1-year randomized, placebo-controlled phase 2 trial for an additional year after they completed treatment. Of the 120 women initially enrolled in the study, 106 women completed treatment and continued into follow-up; 88 women completed 1 year of follow-up. At the beginning of follow-up, groups remained balanced for age, race, and body mass index, but lumbar spine and total hip BMD were increased in prior blosozumab groups, reflecting an anabolic treatment effect. At the end of follow-up, 1 year after discontinuing treatment, lumbar spine BMD remained significantly greater than placebo in women initially treated with blosozumab 270 mg every 2 weeks (Q2W) and blosozumab 180 mg Q2W (6.9% and 3.6% above baseline, respectively). Total hip BMD also declined after discontinuation of treatment but at 1 year after treatment remained significantly greater than placebo in women initially treated with blosozumab 270 mg Q2W and blosozumab 180 mg Q2W (3.9% and 2.6% above baseline, respectively). During follow-up, median serum P1NP was not consistently different between the prior blosozumab groups and placebo. A similar pattern was apparent for median serum C-terminal telopeptide of type 1 collagen (CTx) levels, with more variability. Mean serum total sclerostin concentration increased with blosozumab, indicating target engagement, and declined to baseline after discontinuation. There were no adverse events considered related to prior treatment with blosozumab. Anti-drug antibodies generally declined in patients who had detectable levels during prior treatment. These findings support the continued study of blosozumab as an anabolic therapy for treatment of osteoporosis.