Here we explored whether one such inverse agonist ligand, [Leu<sup>11</sup> ,dTrp<sup>12</sup> ,Trp<sup>23</sup> ,Tyr<sup>36</sup> ]-PTHrP(7-36)NH<sub>2</sub> (IA), can be effective in vivo and thus ameliorate the skeletal abnormalities that occur in transgenic mice expressing the PTHR1-H223R allele of JMC in osteoblastic cells via the collagen-1α1 promoter (C1HR mice).