A Phase-1 Study Comparing Pharmacokinetic and Safety Profiles of Three Different Dose Intervals of Aripiprazole Lauroxil

Aripiprazole lauroxil (AL) is an FDA-approved treatment for schizophrenia. AL is a non-ester prodrug of aripiprazole that results in extended systemic release of aripiprazole after intramuscular (IM) administration. This Phase-1 study evaluated the pharmacokinetics (PK) and safety of a new AL dose (1064 mg)* for 2-month dose intervals. The study also evaluated 4- and 6-week dose intervals of AL at the 441 mg and 882 mg doses, respectively.

A total of 139 patients diagnosed with schizophrenia and stabilized on a first-line antipsychotic (other than aripiprazole) were randomized to one of 3 dose/dose-interval groups: a 4-week interval of AL 441 mg (n = 35), a 6-week interval of AL 882 mg (n = 34), and an 8-week interval of AL 1064 mg IM injection (n = 70). After randomization, AL assignment was open label and administered as gluteal injections over 24 weeks. The total number of injections over this time period was related to the interval: 7 injections for the 441 mg group, 5 for the 882 mg group, and 4 for the 1064 mg group. PK and safety assessments occurred every 2 weeks and extended for an additional 20 weeks after the last injection. Patients continued their prior antipsychotic throughout, such that the safety (but not the PK) findings also reflect a second antipsychotic co-prescribed with AL.

PK findings: administration of AL 1064 mg every 8 weeks and AL 882 mg every 6 weeks provided continuous exposure to aripiprazole. Compared with the AL 441 mg every 4 weeks group, the longer dose-interval groups had consistently higher plasma concentrations for the entirety of the 6- and 8-week dose intervals for the 882 mg and 1064 mg dose groups. Safety findings: the overall safety profile of the group randomized to the 8 week/1064 mg combination was comparable to the 6 week/882 mg and 4 week/441 mg groups. The most common adverse event (AE) for all groups was injection-site reaction (pain). There was no apparent dose-AE signal for extrapyramidal symptoms, akathisia, sedation, or weight gain. In particular, there was no other safety signal identified with the longest interval/highest-dose AL group of 8 weeks/1064 mg.

AL allows for a range of dose/dose-interval combinations. The PK results from this study show that a dosing interval of every 8 weeks for the 1064 mg dose resulted in aripiprazole concentrations within the established therapeutic window for AL. There was no safety signal directing any particular concern to any of the three doses/dose intervals studied. All patients continued their primary antipsychotics without any apparent tolerability issue arising from the addition of the AL injections. The results of this study show that 1064 mg AL may be suitable for a 2-month dose interval. The three doses/dose intervals studied have the potential to help clinicians and patients expand their choice of AL treatment to best meet the needs of the individual patient.