Abaloparatide TFA (BA 058 TFA) is a parathyroid hormone receptor 1 (PTHR1) analogue selected to be a potent and selective activator of the PTHR1 signaling pathway. Abaloparatide TFA enhances Gs/cAMP signaling (EC50 of 0.3 nM) and β-arrestin recruitment (EC50 of 0.9 nM) in MC3T3-E1 osteoblast cells[1][2].

MC3T3-E1 osteoblast cells are treated with 0.01-100 nM of Abaloparatide for 40 min at 37 ℃ in the presence of 0.5 mM IBMX. The results reveals that exposure of cells to Abaloparatide caused a robust elevation of intracellular cAMP levels. Abaloparatide treatment results in a 2.3-fold decrease in EC50 value for cAMP formation compared to teriparatide (EC50s of 0.3 nM and 0.7 nM, respectively)[1]. A dose-dependent stimulation of β-arrestin/PTHR1 interaction is demonstrated by abaloparatide. Consistently, the calculates the EC50 value for abaloparatide is 1.6-fold lower than that of teriparatide (EC50s of 0.9 nM and 1.5 nM, respectively)[1].Abaloparatide efficiently induces a dose-dependent stimulation of PTHR1 internalization with a dose as low as 0.1 nM and reaches maximum stimulation at 100 nM concentration. The EC50 value of 0.8 nM for Abaloparatide[1].

Abaloparatide (1-25 µg/kg; subcutaneous injection; daily; for 12 months; female Sprague-Dawley rats) treatment increases biochemical bone formation markers, histomorphometric indices of bone formation on trabecular, endocortical, and periosteal surfaces. Abaloparatide induces substantial increases in trabecular bone volume and density and improvements in trabecular microarchitecture. Abaloparatide stimulates periosteal expansion and endocortical bone apposition at the tibial diaphysis, leading to marked increases in cortical bone volume and density. Whole-body bone mineral density (BMD) is increasing 25% after 12 months of abaloparatide (25 μg/kg) in osteopenic ovariectomized (OVX) rats[2]. Animal Model: Female Sprague-Dawley rats (age 22 weeks)[2]

[1]. Sahbani K, et al. Abaloparatide exhibits greater osteoanabolic response and higher cAMP stimulation and β-arrestin recruitment than teriparatide. Physiol Rep. 2019 Oct;7(19):e14225. [2]. Varela A, et al. One Year of Abaloparatide, a Selective Activator of the PTH1 Receptor, Increased Bone Formation and Bone Mass in Osteopenic Ovariectomized Rats Without Increasing Bone Resorption. J Bone Miner Res. 2017 Jan;32(1):24-33.