Lasofoxifene (tartrate)

Lasofoxifene (tartrate) is a third-generation, nonsteroidal selective estrogen receptor modulator (SERM).

Estrogen receptors are activated by the hormone estrogen (17β-estradiol). SERMs are characterized by having estrogen agonist action in some tissues while acting as estrogen antagonists in others [1][2].

Lasofoxifene, also known as CP 336,156, is a third-generation, nonsteroidal selective estrogen receptor modulator. Lasofoxifene bound with high affinity to the human estrogen receptor-α with IC50 value of 1.5 nM [1]. Lasofoxifene is also a CB2 inverse agonist [4].

In aged female rats, Lasofoxifene decreased total serum cholesterol and fat body mass, and no uterine hypertrophy was observed. In 5-month-old ovariectomized (OVX) Sprague-Dawley female rats, Lasofoxifene completely prevented OVX-induced increases in body weight gain, total serum cholesterol, and serum osteocalcin. CP-336,156 completely prevented OVX-induced bone loss and inhibited the increased bone turnover associated with estrogen deficiency in lumbar vertebrae, proximal tibiae, and distal femora [1].

In postmenopausal women with osteoporosis, lasofoxifene reduced risks of nonvertebral and vertebral fractures, ER-positive breast cancer, coronary heart disease, and stroke but an increased risk of venous thromboembolic events [2][3].

References:
[1].  Ke HZ, Paralkar VM, Grasser WA, et al. Effects of CP-336,156, a new, nonsteroidal estrogen agonist/antagonist, on bone, serum cholesterol, uterus and body composition in rat models. Endocrinology. 1998 Apr;139(4):2068-76.
[2].  Cummings SR, Ensrud K, Delmas PD, et al. Lasofoxifene in postmenopausal women with osteoporosis. N Engl J Med. 2010 Feb 25;362(8):686-96.
[3].  Gennari L, Merlotti D, Nuti R. Selective estrogen receptor modulator (SERM) for the treatment of osteoporosis in postmenopausal women: focus on lasofoxifene. Clin Interv Aging. 2010 Feb 2;5:19-29.
[4].  Kumar P, Song ZH. CB2 cannabinoid receptor is a novel target for third-generation selective estrogen receptor modulators bazedoxifene and lasofoxifene. Biochem Biophys Res Commun. 2014 Jan 3;443(1):144-9.