Biophysical and Immunological Characterization and In Vivo Pharmacokinetics and Toxicology in Nonhuman Primates of the Anti-PD-1 Antibody Pembrolizumab.

The programmed cell death 1 (PD-1) pathway represents a major immune checkpoint, which may be engaged by cells in the tumor microenvironment to overcome active T-cell immune surveillance. Pembrolizumab (Keytruda®, MK-3475) is a potent and highly selective humanized mAb of the IgG4/kappa isotype designed to directly block the interaction between PD-1 and its ligands, PD-L1 and PD-L2. This blockade enhances the functional activity of T cells to facilitate tumor regression and ultimately immune rejection. Pembrolizumab binds to human and cynomolgus monkey PD-1 with picomolar affinity and blocks the binding of human and cynomolgus monkey PD-1 to PD-L1 and PD-L2 with comparable potency. Pembrolizumab binds both the C'D and FG loops of PD-1. Pembrolizumab overcomes human and cynomolgus monkey PD-L1-mediated immune suppression in T-cell cultures by enhancing IL2 production following staphylococcal enterotoxin B stimulation of healthy donor and cancer patient cells, and IFNγ production in human primary tumor histoculture. Ex vivo and in vitro studies with human and primate T cells show that pembrolizumab enhances antigen-specific T-cell IFNγ and IL2 production. Pembrolizumab does not mediate FcR or complement-driven effector function against PD-1-expressing cells. Pembrolizumab displays dose-dependent clearance and half-life in cynomolgus monkey pharmacokinetic and toxicokinetic studies typical for human IgG4 antibodies. In nonhuman primate toxicology studies, no findings of toxicologic significance were observed. The preclinical data for pembrolizumab are consistent with the clinical anticancer activity and safety that has been demonstrated in human clinical trials.

Phase I trial of intravesical recombinant adenovirus mediated interferon-α2b formulated in Syn3 for Bacillus Calmette-Guérin failures in nonmuscle invasive bladder cancer.

PURPOSE: A phase I trial of intravesical recombinant adenovirus mediated interferon-α2b gene therapy (rAd-IFNα) formulated with the excipient SCH Syn3 was conducted in patients with nonmuscle invasive bladder cancer who had disease recurrence after treatment with bacillus Calmette-Guérin. The primary objective was to determine the safety of rAd-IFNα/Syn3. Secondary end points were demonstrated effective rAd-IFNα gene expression and preliminary evidence of clinical activity at 3 months. MATERIALS AND METHODS: A total of 17 patients with recurrent nonmuscle invasive bladder cancer after bacillus Calmette-Guérin treatment were enrolled in the study. A single treatment of rAd-IFNα (3 × 10(9) to 3 × 10(11) particles per ml) formulated with the excipient Syn3 was administered. Patient safety was evaluated for 12 or more weeks. Efficacy of gene transfer was determined by urine IFNα protein concentrations. Preliminary drug efficacy was determined at 3 months. RESULTS: Intravesical rAd-IFNα/Syn3 was well tolerated as no dose limiting toxicity was encountered. Urgency was the most common adverse event and all cases were grade 1 or 2. rAd-IFNα DNA was not detected in the blood. However, transient low serum IFNα and Syn3 levels were measured. High and prolonged dose related urine IFNα levels were achieved with the initial treatment. Of the 14 patients treated at doses of 10(10) or more particles per ml with detectable urine IFNα, 6 (43%) experienced a complete response at 3 months and 2 remained disease-free at 29.0 and 39.2 months, respectively. CONCLUSIONS: Intravesical rAd-IFNα/Syn3 was well tolerated with no dose limiting toxicity encountered. Dose dependent urinary IFNα concentrations confirmed efficient gene transfer and expression. Intravesical rAd-IFNα/Syn3 demonstrated clinical activity in nonmuscle invasive bladder cancer recurring after bacillus Calmette-Guérin.

SCH 412499: biodistribution and safety of an adenovirus containing P21(WAF-1/CIP-1) following subconjunctival injection in Cynomolgus monkeys.

Monkey studies were conducted for the preclinical safety assessment of SCH 412499, an adenovirus encoding p21, administered by subconjunctival injection prior to trabeculectomy for postoperative maintenance of the surgical opening. Biodistribution of SCH 412499 was minimal and there was no systemic toxicity. Findings included swollen, partially closed or shut eye(s) and transient congestion in the conjunctiva. A mononuclear cell infiltrate was present in the conjunctiva, choroid and other ocular tissues, but completely or partially resolved over time. Electroretinograms and visual evoked potentials revealed no adverse findings. Thus, the findings are not expected to preclude the clinical investigation of SCH 412499.

Site of pegylation and polyethylene glycol molecule size attenuate interferon-alpha antiviral and antiproliferative activities through the JAK/STAT signaling pathway.

Therapeutic pegylated interferon-alphas (IFN-alpha) are mixtures of positional isomers that have been monopegylated at specific sites on the core IFN-alpha molecule. The pegylation results in lower in vitro specific activity associated with the core IFN-alpha molecule that is related to the site of pegylation and size of polyethylene glycol (PEG) attached. We prepared purified, homogeneous, positional pegylation isomers of IFN-alpha2b that were monopegylated using 5-30-kDa linear PEG molecules attached at 7 primary reactive amino acid residues: Cys(1), His(34), Lys(31), Lys(83), Lys(121), Lys(131), and Lys(134). The isomers were evaluated for STAT translocation and antiviral and antiproliferative activity. The site of pegylation strongly influenced activity relative to an IFN-alpha2b control. The highest residual activity was observed with the His(34) positional isomers, and the lowest was observed with the Cys(1) positional isomers. The Lys positional isomers demonstrated intermediate activity, with a general order of Lys(134) > Lys(83) approximately Lys(131) approximately Lys(121) > Lys(31). The progressive relationship between decreased activity and increased PEG size suggests that pegylation may interfere with interaction and binding of IFN-alpha to the IFNAR1-IFNAR2 heterodimeric receptor. The higher specific activity associated with the His(34) positional isomer suggests that this site may be favorable for pegylating IFN-alpha2b molecules.

Development and validation of a kinetic assay for analysis of anti-human interleukin-5 monoclonal antibody (SCH 55700) and human interleukin-5 interactions using surface plasmon resonance.

A method to assess the kinetic interactions of a humanized anti-human interleukin-5 (IL-5) monoclonal antibody (SCH 55700) with native human IL-5 using surface plasmon resonance (SPR) has been developed and validated. Since there are no clearly defined validation requirements for a SPR-based binding kinetic assay, the validation strategy was based on the guidelines stipulated by the International Conference on Harmonization for Analytical Method Validation. Due to the uniqueness of the method, however, proper interpretation of the guidance was critical for establishing a validation plan. Validation was designed to assess repeatability, intermediate precision, specificity, linearity, and robustness which included analysis of baseline stability and reproducibility of ligand immobilization. Additionally, system suitability criteria were established to assure that the assay consistently performs as it was intended. The experimental artifacts that can complicate kinetic analysis using biosensor technology, such as heterogeneity of the ligand, mass transport, and nonspecific binding, were considered during the development of this assay. For each run, replicate concentrations of SCH 55700 were injected randomly over the immobilized surfaces to acquire association- and dissociation-phase data. The data were transformed and double referenced to remove systematic deviations seen in the binding responses. Association and dissociation rates were determined using a bivalent analyte model for curve fitting.

Development of a biosensor-based method for detection and isotyping of antibody responses to adenoviral-based gene therapy vectors.

A biosensor-based assay, using a surface plasmon resonance detection system, was developed to detect and isotype anti-adenoviral antibodies in patients dosed with an adenoviral-based gene therapy vector. In the assay, whole, intact virus was immobilized onto the sensor chip surface. Electron microscopy and monoclonal antibody studies provide evidence that the virus remains intact after immobilization. The patients tested had preexisting serum levels of anti-adenoviral antibodies. A classic anamnestic response was observed in patients dosed with the gene-therapy agent. Isotyping experiments indicated that IgG antibodies predominated in serum even at the predose time point. Analysis of ascites fluid samples from some patients indicated detectable levels of IgA in addition to IgG. Results obtained using the biosensor-based assay corresponded to an existing enzyme-linked immunosorbent assay. The assay was easy to perform and the automated instrument reduced the required "hands on" time. In addition to studying the development of anti-adenoviral antibodies, the techniques described may be applied to virus:receptor interaction studies or antiviral drug:virus interaction studies.

The use of field emission scanning electron microscopy to assess recombinant adenovirus stability.

A field emission scanning electron microscopy (FESEM) method was developed to assess the stability of a recombinant adenovirus (rAd). This method was designed to simultaneously sort, count, and size the total number of rAd viral species observed within an image field. To test the method, a preparation of p53 transgene-expressing recombinant adenovirus (rAd/p53) was incubated at 37 degrees C and the viral particles were evaluated by number, structure, and degree of aggregation as a function of time. Transmission electron microscopy (TEM) was also used to obtain ultrastructural detail. In addition, the infectious activity of the incubated rAd/p53 samples was determined using flow cytometry. FESEM image-analysis revealed that incubation at 37 degrees C resulted in a time-dependent decrease in the total number of detectable single rAd/p53 virus particles and an increase in apparent aggregates composed of more than three adenovirus particles. There was also an observed decrease in both the diameter and perimeter of the single rAd/p53 viral particles. TEM further revealed the accumulation of damaged single particles with time at 37 degrees C. The results of this study demonstrate that FESEM, coupled with sophisticated image analysis, may be an important tool in quantifying the distribution of aggregated species and assessing the overall stability of rAd samples.