To assess the bioequivalence (BE) and relative bioavailability (BA) between a once-daily (QD) extended release formulation of deutetrabenazine and the approved twice-daily (BID) formulation at steady state under fed conditions.

In a phase 1 study (TV50717-BE-10179) using a randomized cross-over design, healthy adult males and females (n=262) received 24 mg QD formulation (test) as a once daily administration and 12 mg BID formulation (reference) as a twice daily administration, each for 7 days in fed state.  Safety was assessed throughout the study and pharmacokinetic (PK) blood sampling occurred on days 4-7. Test-to-reference geometric mean ratios (GMRs) and 90%CIs for BE acceptance limits (80.00% to 125.00%) were computed for PK parameters (area under the plasma concentration curve over 24-hours at steady-state [AUC_0-24hr,ss] and maximum plasma concentration at steady-state [C _max,ss]) of deutetrabenazine, active metabolites, deuterated α-HTBZ and β-HTBZ, and total (α+β)-HTBZ. Relative BA was assessed for C_max,ss of the active metabolites (individually and as a total sum).

The GMRs (90%CIs) for AUC_0-24hr,ss were 115.15% (110.38–120.14%) for deutetrabenazine, 95.40% (94.13–96.69%) for α-HTBZ, 94.13% (92.35–95.94%) for β-HTBZ, and 95.05% (93.67–96.46%) for total (α+β)-HTBZ. GMRs of C_max,ss were 95.09% (90.60-99.80%) for deutetrabenazine, 79.56% (78.21-80.94%) for α-HTBZ, 74.85% (73.13-76.60%) for β-HTBZ and 77.71% (76.26-79.16%) for total (α+β)-HTBZ. No new safety findings emerged in this study.

At steady state, deutetrabenazine administered as the QD formulation was bioequivalent to the approved BID formulation for both AUC and C_max. The active metabolites at steady state were bioequivalent with regard to AUC between the QD and BID formulation; C_max was slightly lower for the QD formulation compared to the BID formulation.