Springer Science and Business Media LLC

The purpose of this study was to develop and validate a simultaneous dissolution and absorption testing tool, the “artificial gut simulator” (AGS), for oral drug formulations. The AGS was constructed using hollow fibers and housed in a 3-mL UV spectrophotometric cuvette that provided a large surface area-to-volume ratio to simulate absorption at a physiological rate. A quasi-steady-state model describing absorption was developed and validated using a high aqueous solubility, BCS-I model compound, caffeine. This model was used to optimize the AGS operating parameters to simulate physiological gastric emptying and caffeine absorption, which was further input into a one-compartment pharmacokinetic (PK) model. The in vivo caffeine plasma concentration-time profiles matched those predicted by the PK model with in vitro input from the AGS. This work provides a framework for establishing an in vitro/in vivo correlation with high-permeability, BCS-II supersaturating drug formulations, which will be explored in the future studies.

mRNA expression profiles had previously been measured in Caco-2 cells (human colonic carcinoma cells) using either custom-designed spotted oligonucleotide arrays or Affymetrix GeneChip oligonucleotide arrays. The Caco-2 cells used were from different clones and were examined under slightly different culture conditions commonly encountered when Caco-2 cells are used as a model tissue for studying intestinal transport and metabolism in different laboratories. In this study, we compared gene expression profiles of Caco-2 cells generated with different arrays to assess the validity of conclusions derived from the 2 independent studies, with a focus on changes in transporter and ion channel mRNA expression levels on Caco-2 cell differentiation. Significant changes in expression levels upon differentiation were observed with 78 genes, with probes common to both arrays. Of these, 18 genes were upregulated and 36 genes were downregulated. The 2 arrays yielded discrepant results for 24 genes, showing significant changes upon differentiation. The results from the 2 arrays correlated well for genes expressed above average levels (r=0.75,P<0.01, n=25) and poorly for genes expressed at low levels (r=0.08,P>0.05, n=25). Overall correlation across the 2 platforms wasr=0.45 (P<0.01) for the 78 genes, with similar results from both arrays. Despite differences in experimental conditions and array technology, similar results were obtained for most genes.

Multiple FDA-approved and clinical-development stage therapeutics include recombinant human hyaluronidase PH20 (rHuPH20) to facilitate subcutaneous administration. As rHuPH20-reactive antibodies potentially interact with endogenous PH20, we investigated rHuPH20 immunogenicity risk through hyaluronidase tissue expression, predicted B cell epitopes, CD4+ T cell stimulation indices and related these to observed clinical immunogenicity profiles from 18 clinical studies. Endogenous hyaluronidase PH20 expression in humans/mice was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR), quantitative RT-PCR, and deep RNA-Seq. rHuPH20 potential T cell epitopes were evaluated in silico and confirmed in vitro. Potential B cell epitopes were predicted for rHuPH20 sequence in silico, and binding of polyclonal antibodies from various species tested on a rHuPH20 peptide microarray. Clinical immunogenicity data were collected from 2643 subjects. From 57 human adult and fetal tissues previously screened by RT-PCR, 22 tissue types were analyzed by deep RNA-Seq. Hyaluronidase PH20 messenger RNA expression was detected in adult human testes. In silico analyses of the rHuPH20 sequence revealed nine T cell epitope clusters with immunogenic potential, one cluster was homologous to human leukocyte antigen. rHuPH20 induced T cell activation in 6–10% of peripheral blood mononuclear cell donors. Fifteen epitopes in the rHuPH20 sequence had the potential to cross-react with B cells. The cumulative treatment-induced incidence of anti-rHuPH20 antibodies across clinical studies was 8.8%. Hyaluronidase PH20 expression occurs primarily in adult testes. Low CD4+ T cell activation and B cell cross-reactivity by rHuPH20 suggest weak rHuPH20 immunogenicity potential. Restricted expression patterns of endogenous PH20 indicate low immunogenicity risk of subcutaneous rHuPH20.

Linagliptin demonstrates substantial nonlinear pharmacokinetics due to its saturable binding to its pharmacological target dipeptidyl peptide 4 (DPP-4), a phenomenon known as target-mediated drug disposition (TMDD). In the current study, we established a novel whole-body physiologically-based pharmacokinetic (PBPK)-TMDD model for linagliptin. This comprehensive model contains plasma and 14 tissue compartments, among which TMDD binding process was incorporated in 9 of them, namely the plasma, kidney, liver, spleen, lung, skin, salivary gland, thymus, and reproductive organs. Our final model adequately captured the concentration-time profiles of linagliptin in both plasma and various tissues in both wildtype rats and DPP4-deficient rats following different doses. The association rate constant (kon) in plasma and tissues were estimated to be 0.943 and 0.00680 nM−1 h−1, respectively, and dissociation rate constant (koff), in plasma and tissues were estimated to be 0.0698 and 0.00880 h−1, respectively. The binding affinity of linagliptin to DPP-4 (Kd) was predicted to be higher in plasma (0.0740 nM) than that in tissue (1.29 nM). When scaled up to a human, this model captured the substantial and complex nonlinear pharmacokinetic behavior of linagliptin in human adults that is characterized by less-than dose-proportional increase in plasma exposure, dose-dependent clearance and volume of distribution, as well as long terminal half-life with minimal accumulation after repeated doses. Our modeling work is not only novel but also of high significance as the whole-body PBPK-TMDD model platform developed using linagliptin as the model compound could be applied to other small-molecule compounds exhibiting TMDD to facilitate their optimal dose selection.

3D printing has emerged as an advanced manufacturing technology in the field of pharmaceutical sciences. Despite much focus on enteral applications, there has been a lack of research focused on potential benefits of 3D printing for parenteral applications such as wound dressings, biomedical devices, and regenerative medicines. 3D printing technologies, including fused deposition modeling, vat polymerization, and powder bed printing, allow for rapid prototyping of personalized medications, capable of producing dosage forms with flexible dimensions based on patient anatomy as well as dosage form properties such as porosity. Considerations such as printing properties and material selection play a key role in determining overall printability of the constructs. These parameters also impact drug release kinetics, and mechanical properties of final printed constructs, which play a role in modulating immune response upon insertion in the body. Despite challenges in sterilization of printed constructs, additional post-printing processing procedures, and lack of regulatory guidance, 3D printing will continue to evolve to meet the needs of developing effective, personalized medicines for parenteral applications.

The availability of structural information on glycosyltransferases is beginning to make structure-based reengineering of these enzymes possible. Mutant glycosyltransferases have been generated that can transfer a sugar residue with a chemically reactive unique functional group to a sugar moiety of glycoproteins, glycolipids, and proteoglycans (glyco-conjugates). The presence of modified sugar moiety on a glycoprotein makes it possible to link bioactive molecules via modified glycan chains, thereby assisting in the assembly of bionanoparticles that are useful for developing the targeted drug delivery system and contrast agents for magnetic resonance imaging. The reengineered recombinant glycosyltransferases also make it possible to (1) remodel the oligosaccharide chains of glycoprotein drugs, and (2) synthesize oligosaccharides for vaccine development.

An intrauterine system (IUS) can be implanted in the uterus and deliver drug directly at the site of pharmacological action. Mirena was the first FDA-approved levonorgestrel (LNG) releasing IUS without an approved generic form. Its 5-year application duration presents challenges for bioequivalence (BE) assessment using the conventional in vivo studies with pharmacokinetic and/or comparative clinical endpoints. Conventionally, along with other conditions, BE could be established if the 90% confidence interval (CI) of the ratio of geometric means of residual LNG at the end of 5 years is within the BE limits of 80.00% and 125.00%. Modeling and simulation were conducted to identify a shortened BE study duration and its corresponding BE acceptance limit that can be used as a surrogate for the conventional limit for a 5-year study. Simulation results suggest that having the 90% CI of the residual LNG 12 months post insertion within 95.00–105.26% would ensure that residual LNG amount at 5 years to be within 80.00–125.00%. This modeling and simulation practice leads to the current BE recommendation: if a test IUS is made of the same material in the same concentration and has the same physical dimensions as the Mirena, its BE could be established by showing (1) comparative physicochemical and mechanical properties; (2) comparative in vitro drug release behavior for 5 years; and (3) performance in a comparative short-term in vivo study and BE based on 90% confidence interval of test and reference ratio of residual LNG to be within 95.00–105.26% at month 12.

Gefitinib (Iressa) is a selective and potent EGFR tyrosine kinase inhibitor. It received an accelerated FDA approval in 2003 for the treatment of patients with nonsmall cell lung cancer (NSCLC) and represents the first-line therapy for NSCLC with EGFR mutations. In the work presented herein, the disposition of gefitinib was investigated extensively in mouse in both plasma and 11 organs (liver, heart, lung, spleen, gut, brain, skin, fat, eye, kidney, and muscle) after a single IV dose of 20 mg/kg. Gefitinib demonstrated extensive distribution in most tissues, except for the brain, and tissue to plasma partition coefficients (K pt) ranged from 0.71 (brain) to 40.5 (liver). A comprehensive whole-body physiologically based pharmacokinetic (PBPK) model of gefitinib in mice was developed, which adequately captured gefitinib concentration-time profiles in plasma and various tissues. Predicted plasma and tissue AUC values agreed well with the values calculated using the noncompartmental analysis (<25% difference). The PBPK model was further extrapolated to humans after taking into account the interspecies differences in physiological parameters. The simulated concentrations in human plasma were in line with the observed concentrations in healthy volunteers and patients with solid malignant tumors after both IV infusion and oral administration. Considering the extensive tissue distribution of gefitinib, plasma concentration may not be an ideal surrogate marker for gefitinib exposure at the target site or organ of toxicity (such as the skin). Since our whole-body PBPK model can predict gefitinib concentrations not only in plasma but also in various organs, our model may have clinical applications in efficacy and safety assessment of gefitinib.

The kidneys and liver are major organs involved in eliminating small-molecule drugs from the body. Characterization of the effects of renal impairment (RI) and hepatic impairment (HI) on pharmacokinetics (PK) have informed dosing in patients with these organ impairments. However, the knowledge about the impact of organ impairment on therapeutic peptides and proteins is still evolving. In this study, we reviewed how often therapeutic peptides and proteins were assessed for the effect of RI and HI on PK, the findings, and the resulting labeling recommendations. RI effects were reported in labeling for 30 (57%) peptides and 98 (39%) proteins and HI effects for 20 (38%) peptides and 55 (22%) proteins. Dose adjustments were recommended for RI in 11 of the 30 (37%) peptides and 10 of the 98 (10%) proteins and for HI in 7 of the 20 (35%) peptides and 3 of the 55 (5%) proteins. Additional actionable labeling includes risk mitigation strategies; for example, some product labels have recommended avoid use or monitor toxicities in patients with HI. Over time, there is an increasing structural diversity of therapeutic peptides and proteins, including the use of non-natural amino acids and conjugation technologies, which suggests a potential need for reassessing the need to evaluate the effect of RI and HI. Herein, we discuss scientific considerations for weighing the risk of PK alteration due to RI or HI for peptide and protein products. We briefly discuss other organs that may affect the PK of peptides and proteins administered via other delivery routes.

Baicalein, a typical flavonoid presented in Scutellariae radix, exhibits a unique metabolic profile during first-pass metabolism: parallel glucuronidation and sulfation pathways, with possible substrate inhibition in both pathways. In this project, we aimed to construct an agent-based model to dynamically represent baicalein pharmacokinetics and to verify the substrate inhibition hypothesis. The model consisted of three 3D spaces and two membranes: apical space (S1), intracellular space (S2), basolateral space (S3), apical membrane (M1), and basolateral membrane (M2). In silico enzymes (UDP-glucuronosyltransferases (UGTs) and sulfotransferases (SULTs)) and binder components were placed in S2. The model was then executed to simulate one-pass metabolism experiments of baicalein. With the implementation of a two-site enzyme design, the simulated results captured the preset qualitative and quantitative features of the wet-lab observations. The feasible parameter set showed that substrate inhibition happened in both conjugation pathways of baicalein. The simulation results suggested that the sulfation pathway was dominant at low concentrations and that SULT was more inclined to substrate inhibition than UGT. Cross-model validation was satisfactory. Our findings were consistent with a previously reported catenary model. We conclude that the mechanisms represented by our model are plausible. Our novel modeling approach could dynamically represent the metabolic pathways of baicalein in a Caco-2 system.