No abstract

Studies in rodents indicate that the disruption of P-glycoprotein (P-gp) function increases drug distribution into the developing fetus and organs such as the brain. To simultaneously and serially evaluate the effect of P-gp activity and inhibition on the tissue distribution of drugs in a more representative animal model, we tested the feasibility of conducting whole-body PET of the pregnant nonhuman primate (Macaca nemestrina). We used 11 C-verapamil as the prototypic P-gp substrate and cyclosporine A (CsA) as the prototypic inhibitor. Methods: Four pregnant macaques (gestational age, 145-159 d; gestational term, 172 d) were imaged after the intravenous administration of 11 C-verapamil (30-72 MBq/kg) before and during intravenous infusion of CsA (12 or 24 mg/kg/h, n 5 2 each). The content of verapamil and its metabolites in plasma samples was determined using a rapid solid-phase extraction method. The plasma and tissue time-radioactivity concentration curves of 11 C were integrated over 0-9 min after each verapamil injection. The tissue or arterial plasma area under the time-concentration curve (AUC tissue / AUC plasma ) served as a measure of the tissue distribution of 11 C radioactivity. CsA effect on 11 C radioactivity distribution was interpreted as P-gp inhibition. The change in the fetal liver AUC ratio served as a reporter of placental P-gp inhibition. Results: CsA effect on tissue distribution of 11 C radioactivity (AUC ratios) did not increase with the mean blood concentration of CsA, indicating a near-maximal P-gp inhibition. CsA increased maternal brain and fetal liver distribution of 11 C radioactivity by 276% 6 88% (P , 0.05) and 122% 6 75% (P , 0.05), respectively. Changes in other measured tissues were not statistically significant. Conclusion: These data demonstrate for the first time, to our knowledge, the feasibility of simultaneous, serial, noninvasive imaging of P-gp activity and inhibition in multiple maternal organs and the placenta in the nonhuman primate. Our findings, consistent with previous data in rodents, indicate that the activity of P-gp in the placenta and the blood-brain barrier is high and that the inhibition of P-gp facilitates drug distribution across these barriers.

Psoriasis is a dermatologic disease of immune origins with no definitive cure. We report the Makati Medical Center experience of utilizing autologous mesenchymal stromal cells (MSCs) for one patient with psoriasis vulgaris (PV) and another with psoriatic arthritis (PA). Patients were educated and gave informed consent, according to the principles of the Declaration of Helsinki. The protocol was approved by the Cellular Transplantation Ethics Committee of the Makati Medical Center. Autologous MSCs were cultured from lipoaspirate and expanded in a clean room class 100 facility (Cellular Therapeutics Center, Makati Medical Center). MSCs were infused intravenously at a dose of 0.5-3.1 million cells/kg after complying with quality control parameters. Psoriasis area and severity index (PASI) evaluations were conducted by third-party dermatologists. The PA patient, who was previously unresponsive to standard treatment modalities, demonstrated a decrease in PASI (from 21.6 to 9.0, mild state after two infusions). No improvements were noted in joint pain until further treatment with etanercept and infliximab. The PV patient, who was previously dependent on methotrexate, showed a decrease in PASI from 24.0 to 8.3 after three infusions; this clinical improvement was sustained for 292 days (9.7 months) without methotrexate. The PV patient illustrated a marginal reduction in serum tumor necrosis factor-a (TNF-a), while significant (3.5-to 5-fold) decreases in reactive oxygen species (ROS) activity were noted. The ROS levels correlated with the clinical improvement of the PV patient. No serious adverse events were noted for either patient as a result of MSC infusions. This report demonstrates safe and tolerable transplantation of autologous MSCs for the treatment of psoriasis and warrants large clinical studies to investigate the long-term safety and efficacy of this approach.

Purpose: Thalidomide has a variety of biological effects that vary considerably according to the species tested. We sought to establish whether differences in pharmacokinetics could form a basis for the species-specific effects of thalidomide.Experimental Design: Mice and rabbits were administered thalidomide (2 mg/kg) p.o. or i.v., and plasma concentrations of thalidomide were measured after drug administration using high performance liquid chromotography. Plasma samples from five multiple myeloma patients over 24 hours after their first dose of thalidomide (200 mg) were similarly analyzed and all data were fitted to a one-compartment model. Metabolites of thalidomide in plasma were identified simultaneously using liquid chromatographymass spectrometry.Results: Plasma concentration-time profiles for the individual patients were very similar to each other, but widely different pharmacokinetic properties were found between patients compared with those in mice or rabbits. Area under the concentration curve values for mice, rabbits, and multiple myeloma patients were 4, 8, and 81 mol/L ⅐ hour, respectively, and corresponding elimination half-lives were 0.5, 2.2, and 7.3 hours, respectively. Large differences were also observed between the metabolite profiles from the three species. Hydrolysis products were detected for all species, and the proportion of hydroxylated metabolites was higher in mice than in rabbits and undetectable in patients. Conclusions:Our results show major interspecies differences in the pharmacokinetics of thalidomide that are related to the altered degree of metabolism. We suggest that the interspecies differences in biological effects of thalidomide may be attributable, at least in part, to the differences in its metabolism and hence pharmacokinetics.

Background and purpose: Changes in tissue P-glycoprotein (P-gp) activity during pregnancy could affect the pharmacokinetics and thus the efficacy and toxicity of many drugs. Therefore, using positron emission tomography (PET) imaging, we tested whether gestational age affects tissue P-gp activity in the pregnant non-human primate, Macaca nemestrina. Experimental approach: Mid-gestational (day 75 Ϯ 13, n = 7) and late-gestational (day 150 Ϯ 10, n = 5) age macaques were imaged after administration of a prototypic P-gp substrate, 11 C-verapamil (13.7-75.4 MBq·kg -1 ), before and during intravenous infusion of a P-gp inhibitor, cyclosporin A (CsA) (12 or 24 mg·kg -1 ·h -1 ). Accumulation of radioactivity in the fetal liver served as a reporter of placental P-gp activity. P-gp activity was expressed as CsA-induced percent change in the ratio of the area (0-9 min) under the 11 C-radioactivity concentration-time curve in the tissue (AUCtissue) to that in the maternal plasma (AUCplasma). Key results: The CsA-induced change in AUCfetal liver/AUCmaternal plasma of 11 C-radioactivity significantly increased from mid-(35 Ϯ 25%) to late gestation (125 Ϯ 66%). Likewise, the CsA-induced change in AUCmaternal brain/AUCplasma increased from mid-(172 Ϯ 80%) to late gestation (337 Ϯ 148%). The AUC ratio for the other maternal tissues was not significantly affected. Neither the CsA blood concentrations nor the level of circulating 11 C-verapamil metabolites were significantly affected by gestational age. Conclusions and implications: P-gp activity at the blood-brain barrier and the placental barrier in the macaque increased with gestational age. If replicated in humans, the exposure of the fetus and maternal brain to P-gp substrate drugs, and therefore their efficacy and toxicity, will change during pregnancy.