If we utilize this compartment again as soon as it becomes available and space the doses correctly, we should be able to use a more frequent dose in a short time frame thus approximating “oral infusion.” Several researches

have reported the GI transit time of small lab animals [13–22]. Based on those reported values and ABT-263 price in-house data, the GI transit time for a rat is anywhere from 2.5hrs to 12hrs. The previously tandem Inhibitors,research,lifescience,medical dose work we have done used a fixed dose interval of 2.5hrs as a starting interval to test the theory. It is believed that an interval of two to three hours should be sufficient to separate two doses from each compartment. Thus, an absorbable amount of drug can be dosed every two to three hours as a tandem dose without having significant dose overlap. This tandem dose approach provided several advantages compared with regular b.i.d. Inhibitors,research,lifescience,medical or t.i.d. doses. First, this approach eliminates the need for overtime and late night shifts. Second, unlike regular b.i.d. or t.i.d. doses that often only improve AUC for drugs with higher clearance, this approach allows for continuous

absorption of drug. This allows the drug concentration in plasma to build up via accumulation, Inhibitors,research,lifescience,medical resulting in a much higher Cmax which is critical for target proof of concept (POC) and safety evaluation. Figure 1 Tandem dose scheme. The impact on AUC and Cmax of a hypothetical compound by a 3X tandem dose with a 2.5hrs Inhibitors,research,lifescience,medical interval versus that of a t.i.d. dose is illustrated in Figure 2. The PK parameters used for the hypothetical compound are representative of several internal preclinical candidates. The compound is assumed to have an oral bioavailability of 30% with a volume of distribution (Vd) of 1L/Kg and medium clearance (CL) in rat of 20ml/min/Kg. A previously established in-house oral model based on the Bateman Inhibitors,research,lifescience,medical equation was used for the simulation [12]. This approach has been proven to be very effective in the preclinical setting. We have demonstrated that with this oral tandem dose, higher exposures

(Cmax and AUC) are achievable without employing enabling formulations and while conserving the amount of active pharmaceutical ingredient required [12]. Most importantly, no extra staffing resources were needed. Figure 2 PK simulation of tandem versus regular t.i.d. dose. Despite the success of this GI transit time-based tandem dosing strategy, one question isothipendyl remained. The optimum tandem dose interval had yet to be fully studied. A fixed 2.5hrs dosing interval was used in the previous study and successfully demonstrated the theory. However, in order to take full advantage of this novel strategy, a better understanding of dose versus interval was needed. In both studies, a low solubility compound was tested with tandem dose. Compound 1 is a potent phosphodiesterase 2 (PDE2) inhibitor. PDE2 is one of the most important downstream targets of phosphodiesterase.