The purpose of this study is to evaluate the effects of single and multiple doses of ABCL635 administered by subcutaneous (SC) injection to healthy men and to postmenopausal women with or without any vasomotor symptoms (VMS) or hot flashes, and to postmenopausal women with moderate-to-severe VMS associated with menopause. The safety, tolerability, pharmacokinetic (PK) and pharmacodynamic (PD) parameters of ABCL635 will be assessed in all study participants; the effects on frequency and severity of VMS will be assessed in postmenopausal women who experience moderate-to-severe symptoms.