Christopher Matheny

An orally active calcium-sensing receptor antagonist that transiently increases plasma concentrations of PTH and stimulates bone formation

Daily subcutaneous administration of exogenous parathyroid hormone (PTH) promotes bone formation in patients with osteoporosis. Here we describe two novel, short-acting calcium-sensing receptor antagonists (SB-423562 and its orally bioavailable precursor, SB-423557) that elicit transient PTH release from the parathyroid gland in several preclinical species and in humans. In an ovariectomized rat model of bone loss, daily oral administration of SB-423557 promoted bone formation and improved parameters of bone strength at lumbar spine, proximal tibia and midshaft femur. Chronic administration of SB-423557 did not increase parathyroid cell proliferation in rats. In healthy human volunteers, single doses of intravenous SB-423562 and oral SB-423557 elicited transient elevations of endogenous PTH concentrations in a profile similar to that observed with subcutaneously administered PTH. Both agents were well tolerated in humans. Transient increases in serum calcium, an expected effect of increased parathyroid hormone concentrations, were observed post-dose at the higher doses of SB-423557 studied. These data constitute an early proof of principle in humans and provide the basis for further development of this class of compound as a novel, orally administered bone-forming treatment for osteoporosis.

Translational development of an ADAMTS-5 antibody for osteoarthritis disease modification

OBJECTIVE/METHOD Aggrecanase activity, most notably ADAMTS-5, is implicated in pathogenic cartilage degradation. Selective monoclonal antibodies (mAbs) to both ADAMTS-5 and ADAMTS-4 were generated and in vitro, ex vivo and in vivo systems were utilized to assess target engagement, aggrecanase inhibition and modulation of disease-related endpoints with the intent of selecting a candidate for clinical development in osteoarthritis (OA). RESULTS Structural mapping predicts the most potent mAbs employ a unique mode of inhibition by cross-linking the catalytic and disintegrin domains. In a surgical mouse model of OA, both ADAMTS-5 and ADAMTS-4-specific mAbs penetrate cartilage following systemic administration, demonstrating access to the anticipated site of action. Structural disease modification and associated alleviation of pain-related behavior were observed with ADAMTS-5 mAb treatment. Treatment of human OA cartilage demonstrated a preferential role for ADAMTS-5 inhibition over ADAMTS-4, as measured by ARGS neoepitope release in explant cultures. ADAMTS-5 mAb activity was most evident in a subset of patient-derived tissues and suppression of ARGS neoepitope release was sustained for weeks after a single treatment in human explants and in cynomolgus monkeys, consistent with high affinity target engagement and slow ADAMTS-5 turnover. CONCLUSION This data supports a hypothesis set forth from knockout mouse studies that ADAMTS-5 is the major aggrecanase involved in cartilage degradation and provides a link between a biological pathway and pharmacology which translates to human tissues, non-human primate models and points to a target OA patient population. Therefore, a humanized ADAMTS-5-selective monoclonal antibody (GSK2394002) was progressed as a potential OA disease modifying therapeutic.

Quantitation OF ARGS aggrecan fragments in synovial fluid, serum and urine from osteoarthritis patients

OBJECTIVE To characterise ARGS neoepitope concentrations in various matrices from patients with knee osteoarthritis (OA) and assess performance of an immunoassay to facilitate clinical development of therapeutics affecting the A disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS-5) pathway. DESIGN Matched sera, urine, and synovial fluid (SF) (surgical subjects only) were collected from healthy subjects, subjects with knee OA (non-surgical OA), and OA subjects undergoing total knee replacement (OA-TKR; n = 20 per group). Diurnal and inter-day variation was evaluated in the non-surgical OA group over 3 separate visits. Serum and urine samples were collected on two visits for the OA-TKR group with SF taken only at the time of surgery. ARGS neoepitope was quantitated using an optimized immunoassay. RESULTS Serum ARGS neoepitope concentrations were elevated in OA-TKR subjects compared to non-surgical OA subjects (P = 0.005) and healthy subjects (P = 0.0002). Creatinine corrected urinary ARGS neoepitope concentrations were more variable, but were also elevated in the OA-TKR subjects compared to healthy subjects (P = 0.008). No significant diurnal effect or inter-day variance was observed in serum or urine. Serum ARGS neoepitope concentrations correlated with age (P = 0.0252) but not with total number of joints with OA involvement. SF ARGS neoepitope concentrations correlated with Western Ontario and MacMaster OA Index (WOMAC) stiffness score (P = 0.04) whereas a weaker, non-significant trend towards positive correlation with combined WOMAC score and the number of concurrent joints was observed. CONCLUSIONS This study utilized a sensitive and robust assay to evaluate ARGS neoepitope concentrations in various matrices in OA patients and healthy volunteers. ARGS neoepitope appears promising as a prognostic/stratification marker to facilitate patient selection and as an early pharmacodynamic marker for OA therapeutic trials.

Optimizing the in vitro and clinical assessment of drug interaction risk by understanding co-medications in patient populations

Introduction: Pharmacokinetic drug interactions resulting from the inhibition of drug elimination mechanisms are of concern in drug development due to the clinical risk associated with elevated drug concentrations. Advances in understanding the mechanistic basis of these drug interactions has resulted in the widespread application of mechanistic in vitro assays and the conduct of clinical drug interaction studies to predict and quantify the risks in drug development. Areas covered: The authors investigate co-medication prescriptions in target patient populations and characterize the mechanistic basis and clinical impact of known co-medication drug interactions. This has enabled identification of critical mechanistic in vitro studies and provided options to manage co-medication use in clinical studies. Furthermore, they demonstrate, for the pharmaceutical scientist, how improved understanding of the drug interactions risks associated with key medications in a target therapeutic area, can help prioritize the conduct of in vitro data and optimize the timing of the clinical drug interaction studies required to characterize drug interaction risks. Expert opinion: This approach provides a more targeted strategy to drug interaction data generation, as routine application of assays may provide limited impact on drug progression decisions. Assessing co-medications in the target patient population enables early discharge of the safety risks associated with drug interactions and reduced investment in drug interaction studies.

Inhibition of Intestinal OATP2B1 by the Calcium Receptor Antagonist Ronacaleret Results in a Significant Drug-Drug Interaction by Causing a 2-Fold Decrease in Exposure of Rosuvastatin

Rosuvastatin is a widely prescribed antihyperlipidemic which undergoes limited metabolism, but is an in vitro substrate of multiple transporters [organic anion transporting polypeptide 1B1 (OATP1B1), OATP1B3, OATP1A2, OATP2B1, sodium-taurocholate cotransporting polypeptide, breast cancer resistance protein (BCRP), multidrug resistance protein 2 (MRP2), MRP4, organic anion transporter 3]. It is therefore frequently used as a probe substrate in clinical drug-drug interaction (DDI) studies to investigate transporter inhibition. Although each of these transporters is believed to play a role in rosuvastatin disposition, multiple pharmacogenetic studies confirm that OATP1B1 and BCRP play an important role in vivo. Ronacaleret, a drug-development candidate for treatment of osteoporosis (now terminated), was shown to inhibit OATP1B1 in vitro (IC50 = 11 µM), whereas it did not inhibit BCRP. Since a DDI risk through inhibition of OATP1B1 could not be discharged, a clinical DDI study was performed with rosuvastatin before initiation of phase II trials. Unexpectedly, coadministration with ronacaleret decreased rosuvastatin exposure by approximately 50%, whereas time of maximal plasma concentration and terminal half-life remained unchanged, suggesting decreased absorption and/or enhanced first-pass elimination of rosuvastatin. Of the potential in vivo rosuvastatin transporter pathways, two might explain the observed results: intestinal OATP2B1 and hepatic MRP4. Further investigations revealed that ronacaleret inhibited OATP2B1 (in vitro IC50 = 12 µM), indicating a DDI risk through inhibition of absorption. Ronacaleret did not inhibit MRP4, discharging the possibility of enhanced first-pass elimination of rosuvastatin (reduced basolateral secretion from hepatocytes into blood). Therefore, a likely mechanism of the observed DDI is inhibition of intestinal OATP2B1, demonstrating the in vivo importance of this transporter in rosuvastatin absorption in humans.

Response to ERBB3-Directed Targeted Therapy in NRG1-Rearranged Cancers

NRG1 rearrangements are oncogenic drivers that are enriched in invasive mucinous adenocarcinomas (IMA) of the lung. The oncoprotein binds ERBB3-ERBB2 heterodimers and activates downstream signaling, supporting a therapeutic paradigm of ERBB3/ERBB2 inhibition. As proof of concept, a durable response was achieved with anti-ERBB3 mAb therapy (GSK2849330) in an exceptional responder with an NRG1-rearranged IMA on a phase I trial (NCT01966445). In contrast, response was not achieved with anti-ERBB2 therapy (afatinib) in four patients with NRG1-rearranged IMA (including the index patient post-GSK2849330). Although in vitro data supported the use of either ERBB3 or ERBB2 inhibition, these clinical results were consistent with more profound antitumor activity and downstream signaling inhibition with anti-ERBB3 versus anti-ERBB2 therapy in an NRG1-rearranged patient-derived xenograft model. Analysis of 8,984 and 17,485 tumors in The Cancer Genome Atlas and MSK-IMPACT datasets, respectively, identified NRG1 rearrangements with novel fusion partners in multiple histologies, including breast, head and neck, renal, lung, ovarian, pancreatic, prostate, and uterine cancers.Significance: This series highlights the utility of ERBB3 inhibition as a novel treatment paradigm for NRG1-rearranged cancers. In addition, it provides preliminary evidence that ERBB3 inhibition may be more optimal than ERBB2 inhibition. The identification of NRG1 rearrangements across various solid tumors supports a basket trial approach to drug development. Cancer Discov; 8(6); 686-95. ©2018 AACR.See related commentary by Wilson and Politi, p. 676This article is highlighted in the In This Issue feature, p. 663.

Non invasive imaging assessment of the biodistribution of GSK2849330, an ADCC and CDC optimized anti HER3 mAb, and its role in tumor macrophage recruitment in human tumor-bearing mice

The purpose of this work was to use various molecular imaging techniques to non-invasively assess GSK2849330 (anti HER3 ADCC and CDC enhanced ‘AccretaMab’ monoclonal antibody) pharmacokinetics and pharmacodynamics in human xenograft tumor-bearing mice. Immuno-PET biodistribution imaging of radiolabeled 89Zr-GSK2849330 was assessed in mice with HER3 negative (MIA-PaCa-2) and positive (CHL-1) human xenograft tumors. Dose dependency of GSK2849330 disposition was assessed using varying doses of unlabeled GSK2849330 co-injected with 89Zr-GSK2849330. In-vivo NIRF optical imaging and ex-vivo confocal microscopy were used to assess the biodistribution of GSK2849330 and the HER3 receptor occupancy in HER3 positive xenograft tumors (BxPC3, and CHL-1). Ferumoxytol (USPIO) contrast-enhanced MRI was used to investigate the effects of GSK2849330 on tumor macrophage content in CHL-1 xenograft bearing mice. Immuno-PET imaging was used to monitor the whole body drug biodistribution and CHL-1 xenograft tumor uptake up to 144 hours post injection of 89Zr-GSK2849330. Both hepatic and tumor uptake were dose dependent and saturable. The optical imaging data in the BxPC3 xenograft tumor confirmed the tumor dose response finding in the Immuno-PET study. Confocal microscopy showed a distinguished cytoplasmic punctate staining pattern within individual CHL-1 cells. GSK2849330 inhibited tumor growth and this was associated with a significant decrease in MRI signal to noise ratio after USPIO injection and with a significant increase in tumor macrophages as confirmed by a quantitative immunohistochemistry analysis. By providing both dose response and time course data from both 89Zr and fluorescently labeled GSK2849330, complementary imaging studies were used to characterize GSK2849330 biodistribution and tumor uptake in vivo. Ferumoxytol-enhanced MRI was used to monitor aspects of the immune system response to GSK2849330. Together these approaches potentially provide clinically translatable, non-invasive techniques to support dose optimization, and assess immune activation and anti-tumor responses.

Development of an ultra-sensitive assay for the determination of an aminoalkyl glucosaminide 4-phosphate, GSK1795091, in plasma to support a first time in human study

GSK1795091 (or CRX-601), an aminoalkyl glucosaminide 4-phosphate, is a potent TLR4 agonist in clinical development for the treatment of cancer. Bioanalysis of GSK1795091 is challenging as extremely low doses (<1 μg) are administered in clinical settings, requiring an assay with a quantitation limit of 2 pg mL−1 or below. Other challenges associated with the bioanalysis of GSK1795091 include carryover and nonspecific binding issues. Due to these compound characteristics and the lack of precedence, extensive method development was performed to address these challenges. A novel extraction protocol was developed that included sample clean up with an Ostro™ pass-through sample preparation plate and a double chemical derivatization approach targeting hydrophilic functional moieties. The method was validated over the concentration range of 2 to 100 pg mL−1 and employed to determine the exposure of GSK1795091 in a first time in human clinical study. Incurred sample reanalysis was also included and the results agreed with those of the original analysis. The method was found to be precise, accurate and robust, and the low LOQ was critical to adequately support clinical PK assessments.

Abstract 1192: Preclinical evaluation of HER3 mutations and rational combinations with AKT inhibition in enhancing anti-tumor activity of HER3 inhibition in gastric cancer

Molecular activating events involving the ERBB RTK family members (EGFR (ERBB1), HER2 (ERBB2), HER3 (ERBB3), HER4 (ERBB4)) drive oncogenesis by inducing proliferation, invasion and survival primarily through RAS/MAPK and PI3K/AKT signaling pathways in several cancers. The clinical successes of HER2 directed therapies are well known in breast cancer and more recently, in gastric cancer. However, resistance develops invariably and gastric cancer continues to be a largely unmet disease necessitating novel therapeutic interventions. Recent reports have highlighted HER3 as an emerging target as it is frequently overexpressed, mutated, preferentially dimerizes with HER2 to activate signaling and is induced as a result of de novo or acquired resistance to PI3K-AKT, MAPK and RTK pathway inhibitors. We explored the utility of an ADCC and CDC enhanced potent anti-HER3 therapeutic antibody (GSK2849330) as a single agent or in combination with a selective small molecule AKT inhibitor (GSK2110183) in patient-derived xenograft (PDX) models of gastric cancer. A panel of 15 HER3 mutant and 4 HER3 wildtype PDX models was screened in vivo for responses to GSK2849330 as measured by% tumor growth inhibition (%TGI). Several models were characterized for other molecular alterations (e.g. HER2, PTEN, HER3, etc.) and represented various subsets of gastric cancer. As a single agent administered at 25mg/kg IP BIW, GSK2849330 was modestly effective (TGI ≥ 50%) in 2/15 mutant and 2/4 wildtype models. While context is likely to matter to drive dependence on HER3, no obvious predictive markers were observed. Furthermore, we evaluated the effect of combination therapy with an AKT inhibitor (GSK2110183) administered at 60mg/kg PO QD in a HER3 wildtype, PTEN deficient model. This resulted in significant durable tumor growth inhibition (∼94% TGI) with improved survival and noticeable tumor regression in a few mice in the combination treatment group relative to either single agent groups. Tumor samples collected at the end of the study showed pronounced pharmacodynamic modulation of p-AKT and p-HER3, demonstrating on target activity of these agents. Taken together, our findings suggest that modest anti-tumor activity was elicited by GSK2849330 as monotherapy in select gastric PDX models with no clear associations between response and HER3 mutations or other known markers. However, robust durable activity was observed upon combination with GSK2110183. To our knowledge, this is the first in vivo evidence supporting the rational combination of a selective AKT inhibitor (GSK2110183) and an anti-HER3 therapeutic antibody (GSK2849330), both of which are actively undergoing clinical trials and warrant further investigation in gastric cancer. Citation Format: Gopi Ganji, Sherry Qin, Crystal Qin, Neil Clarke, Carolyn Buser-Doepner, Christopher Matheny, Rakesh Kumar, Biju Mangatt. Preclinical evaluation of HER3 mutations and rational combinations with AKT inhibition in enhancing anti-tumor activity of HER3 inhibition in gastric cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1192.