Pharmacokinetics and Safety of an Improved Oral Formulation of Paltusotine, a Selective, Non-Peptide Somatostatin Receptor 2 (SST2) Agonist for the Treatment of Acromegaly Open Access

Depot injection formulations of peptide somatostatin receptor ligands (SRLs) are routinely used to treat acromegaly and neuroendocrine tumors (NETs). Paltusotine (CRN00808), an orally administered small molecule nonpeptide selective somatostatin receptor 2 (SST2) agonist has been shown to maintain GH and IGF-1 levels in acromegaly patients previously on depot SRLs (ACROBAT Edge NCT03789656). In this study, a capsule formulation was used, which did not exhibit dose proportional pharmacokinetics (PK) at doses >40 mg, required a 2-hour post-dose fast in overnight fasted patients, and had the potential for reduced bioavailability when taken with proton-pump inhibitors (PPI). A spray-dried dispersion (SDD) tablet formulation was developed with improved solubility in the physiological pH range and its performance was evaluated in healthy volunteers. Male and female healthy volunteers who met inclusion/exclusion criteria were enrolled in a single-center Phase 1 study (ANZCTR registration ACTRN12619001562167). A Cohort of 12 subjects was administered a single dose of paltusotine in a four-period cross-over design. Periods 1 and 2 assessed the effect of lansoprazole (a PPI) on PK of 20 mg dose of paltusotine SDD tablets. In Period 3, 20 mg dose of paltusotine SDD tablets was co-administered with a high fat, high-calorie meal. In Period 4, a 60 mg dose of paltusotine SDD tablets was administered to assess dose proportionality. In a separate cohort of subjects (n=12; also, a 4-period cross-over design), the relative bioavailability of capsules and SDD tablets was assessed, and the effect of food administration 0.5, 1, and 2 hour post-dose was evaluated. Subsequently, in another cohort of 12 subjects (a 3-period cross-over design), dose proportionality of the SDD tablets was evaluated at 40 mg and 80 mg dose with a 1-hour post-dose fast. A 4 hours post-dose fast was also assessed for the 80 mg dose. Pharmacokinetics and safety of paltusotine were evaluated. Paltusotine was generally well tolerated in this study. SDD tablets exhibited dose proportional increase in total systemic exposure (AUC) up to a dose of 80 mg. Healthy volunteers pretreated with the PPI, lansoprazole (15 mg bid for 3 days), and co-administered with paltusotine SDD tablets exhibited a small decrease (approximately 25%) in systemic exposure to paltusotine compared with the same subjects that had washed out from the PPI-pretreatment. SDD tablets exhibited significant reduction in systemic exposure when co-administered with a high-fat, high-calorie meal. However, the SDD formulation was less sensitive to timing of post-dose food administration compared to the capsule formulation. These data suggest that the SDD tablet formulation of paltusotine improves flexibility in dose administration, can be co-administered with PPIs and other agents that increase stomach pH, and reduces the post-dose fasting requirement.