(T1030-11-72) Enhancing the Oral Bioavailability of a Novel Anti-tuberculosis Drug Candidate, Quabodepistat, via Cocrystallization and Mechanistic Analysis of Differences in Bioavailability between Two Cocrystals

Purpose: Enhancing oral bioavailability by cocrystals using a novel anti-tuberculosis drug candidate, quabodepistat. Identifying the mechanism of the differences in bioavailability between two cocrystals via in vitro dissolution study.

Methods: Cocrystal with 2-hydroxybenzoic acid, 2HBA (quabodepistat-2HBA) and cocrystal with 2,5-dihydroxybenzoic acid, 2,5DHBA (quabodepistat-2,5DHBA) were prepared by anti-solvent crystallization method. Bioavailability studies were carried out using five fasted beagle dogs. The free form and the two cocrystals corresponding to 100 mg of quabodepistat were respectively filled into a hard gelatin capsule along with lactose monohydrate as a filler, then orally dosed to the dogs. Blood samples were collected at 0.5, 1, 2, 4, 8, 12, and 24 hours after oral administration and quabodepistat was quantified by LC-MS/MS.
Dissolution studies were conducted with pH 1.2 media, which contain 1% w/w hypromellose and set at 37ºC using MicroDISS Profiler with the stirring speed of 150 rpm. The free form or two different cocrystals corresponding to 5 mg of quabodepistat was added respectively into 20 mL of dissolution media. Dissolution samples containing either free form of quabodepistat or two coformers (2,5DHBA or 2HBA) was analyzed by UHPLC from 0.5 to 120 min. As the coformers are highly soluble and not precipitated in the dissolution media, the dissolution profiles of coformers were regarded as that of two cocrystals.
The pH-shifting dissolution studies were conducted using two media; 0.1 N HCL and pH 6.8 buffers at 37ºC using MicroDISS Profiler with the stirring speed of 150 rpm. The two different cocrystals corresponding to 20 mg of quabodepistat was added respectively into 8 mL of 0.1N HCL and stirred for 15 min, then the pH was adjusted at 6.8 with 12 mL of 0.20 M tribasic sodium phosphate. Dissolution samples were collected from 0.25 to 15 min after the medium pH has changed to 6.8 and quantified by UHPLC.

Results: As a results of the bioavailability studies in beagle dogs, both of the cocrystals did enhance bioavailability compared to the free form. The AUC of quabodepistat-2,5DHBA and quabodepistat-2HBA were 4.1-fold and 5.9-fold higher than those of free form, respectively (Fig. 1). The extent of bioavailability of quabodepistat-2HBA was 1.4 times higher than that of quabodepistat-2,5DHBA.
In order to elucidate the difference in bioavailability between two cocrystals, dissolution studies in pH 1.2 media were conducted. As a result, both of the cocrystals demonstrated similar supersaturated dissolution profile in pH 1.2 media (Fig. 2, left axis), however, there was a difference in % dissolved between the two cocrystals. Namely, quabodepistat-2HBA dissolved slower than quabodepistat-2,5DHBA (Fig. 2, right axis). More specifically, the entire quantity of quabodepistat-2,5DHBA was dissolved within 20 min, while quabodepistat-2HBA was not completely dissolved even after 2 hours. From the dissolution studies, it was suggested that quabodepistat-2HBA was poorly soluble and more stable than quabodepistat-2,5DHBA in pH 1.2. In order to find out a relevant dissolution method that correlates well with the bioavailability results in beagle dogs,　pH-shift dissolution studies which mimics the dynamic pH change from the stomach to the small intestine was conducted. As a result, quabodepistat-2HBA demonstrated supersaturation after the pH was raised to 6.8, while quabodepistat-2,5DHBA did not demonstrate supersaturation (Fig. 3). This result was in good agreement with the results of the bioavailability studies in beagle dogs. It is considered that more quantity of orally administrated quabodepistat-2HBA were remained in its cocrystal form while being transferred to the small intestine in comparison with quabodepistat-2,5DHBA.

Conclusion: Bioavailability of quabodepistat has been successfully enhanced by cocrystallization either with 2,5DHBA or 2HBA. Difference in bioavailability of the two cocrystals was considered due to the different stability in terms of the cocrystal form in the stomach. In the dissolution study of cocrystal, evaluating the concentration – time profiles of coformers was very informative as dissolution behavior of cocrystal was not elucidated only by the drug concentration.

Fig. 1. Serum concentration-time profiles in fasted beagle dogs after oral administration of quabodepistat (free form) and cocrystals at a dose of 100 mg/body as drug substance.

Fig. 2. Concentration – time profiles of quabodepistat from cocrystals (left axis) and dissolved % of cocrystals (right axis) in pH 1.2 medium containing 1% w/w hypromellose at 37°C.

Fig. 3. Concentration – time profiles of quabodepistat from cocrystals by pH-shifting dissolution method at 37°C.