733. Pharmacokinetic–Pharmacodynamic (PK–PD) Analyses for Alanine Aminotransferase (ALT) Using Phase 3 Data From Omadacycline (OMC)-Treated Patients

Abstract Background OMC, an aminomethylcycline structurally related to tetracycline agents, was recently approved by the US FDA for the treatment of adult patients with ABSSSI (IV-to-PO and PO regimens) and CABP (IV-to-PO regimen). To better understand exposure-related concerns for ALT increase, PK-PD relationships for ALT were evaluated using data from OMC-treated patients enrolled in three Phase 3 studies. Methods Repeated-measures multiple linear regression was used to evaluate factors predictive of ALT, including different OMC total-drug AUC measures prior to each ALT, with interactions and covariates selected stepwise. Using a final AIC-optimized model, predicted percent probabilities of ALT elevation >1, 1.5, 2, 3, 5, and 10 × upper limit of normal (ULN) at any time post-baseline and up to 2 days after the end of therapy were calculated among analysis patients for fixed post-baseline OMC AUC measures, and among simulated patients after IV-to-PO and PO dosing regimens. Results The final model, developed using data from 327 patients with PK, included increased prior cumulative AUC among males, increased baseline gamma-glutamyl transferase, and study (ABSSSI, PO only) as factors predictive of increased ALT (P < 0.0001). However, the model-predicted impact of OMC across fixed average daily AUC values on ALT elevation endpoints of >1, 1.5, 2, 3, 5, and 10 × ULN was minimal (Figure 1), even for males despite the interaction with AUC (Figure 2). Among all patients, the estimated increases in percent probabilities for the 90th percentile of AUC relative to zero AUC were 5.81, 5.20, 1.53, 0.61, 0.31, and 0%, respectively, and ≤11.5, 7.76, 8.33, 1.31, 1.31, and 0%, respectively, across single variable patient subsets. Percent probabilities of ALT elevation endpoints were within 2.84% when comparing simulated and observed patients after administration of OMC IV-to-PO and PO dosing regimens (Figure 3). Conclusion A statistically significant relationship between an increase in ALT and increase in OMC AUC for males in the presence of other factors was found. However, increases in model-predicted ALT elevation endpoints across fixed OMC AUC values, or among simulated patients after administration of OMC IV-to-PO and PO dosing regimens relative to observed patients, were minimal. Disclosures All authors: No reported disclosures.