The Effect of Itraconazole on the Pharmacokinetics of Vepdegestrant, a PROteolysis TArgeting Chimera Estrogen Receptor Degrader, in Healthy Adult Participants.

PURPOSE Vepdegestrant (ARV-471) is an orally administered PROteolysis TArgeting Chimera estrogen receptor (ER) degrader that directly binds an E3 ligase and ER to trigger ubiquitination and subsequent proteasomal degradation of ER. Based on findings from a first-in-human phase 1/2 trial, vepdegestrant 200 mg once daily was selected as the recommended phase 3 dose and was evaluated in the phase 3 clinical study VERITAC-2 (NCT05654623) for the treatment of patients with ER-positive human epidermal growth factor receptor 2-negative breast cancer. Vepdegestrant is a substrate of cytochrome P450 (CYP)3A4 in vitro; therefore, its plasma exposure may increase when coadministered with CYP3A4 inhibitors, such as the strong index CYP3A4 inhibitor itraconazole. This study evaluated the effect of itraconazole on the pharmacokinetics (PK) and safety of vepdegestrant in healthy adults.

METHODS During this phase 1, open-label, 2-period, fixed-sequence study (NCT05538312), participants received 2 doses of vepdegestrant and multiple doses of itraconazole. In period 1, participants received a single dose of vepdegestrant 200 mg under fed conditions followed by a washout period of at least 10 days. In period 2, participants received itraconazole 200 mg once daily under fasted conditions on days 1-11 and a single dose of vepdegestrant 200 mg under fed conditions on day 5 with concomitant itraconazole administration. Plasma samples were collected predose and serially following each vepdegestrant dose. PK parameters calculated for vepdegestrant and its epimer metabolite, ARV-473, included area under the plasma concentration-time curve from time 0 extrapolated to infinity (AUCinf) and maximum plasma concentration (Cmax). Safety was monitored throughout the study.

FINDINGS A total of 12 healthy adult participants received vepdegestrant with (test) and without (reference) itraconazole. The vepdegestrant test/reference ratios of the adjusted geometric means (90% confidence intervals) for AUCinf and Cmax were 168.9% (157.7-180.9) and 152.2% (136.9-169.2), respectively. Similar increases in exposure were observed for ARV-473. All adverse events were mild or moderate, and no participants discontinued from the study due to adverse events.

IMPLICATIONS Coadministration of multiple doses of itraconazole, a strong CYP3A4 inhibitor, increased vepdegestrant exposure by 69%, suggesting the involvement of CYP3A4-mediated metabolism, albeit not predominantly, in vepdegestrant elimination.