Liver injury in cynomolgus monkeys following intravenous and intrathecal scAAV9 gene therapy delivery.

Hepatotoxicity associated with intravenous/intrathecal adeno-associated virus (AAV) gene therapy has been observed in preclinical species and patients. In nonhuman primates, hepatotoxicity following self-complementary AAV9 administration varies from asymptomatic transaminase elevation with minimal to mild microscopic changes to symptomatic elevations of liver function and thromboinflammatory markers with microscopic changes consistent with marked hepatocellular necrosis and deteriorating clinical condition. These transient acute liver injury marker elevations occur from 3-4 days post intravenous administration to ∼2 weeks post intrathecal administration. No transaminase elevation or microscopic changes were observed with intrathecal administration of empty capsids or a "promoterless genome" vector, suggesting that liver injury after cerebrospinal fluid dosing in nonhuman primates is driven by viral transduction and transgene expression. Co-administration of prednisolone after intravenous or intrathecal dosing did not prevent liver enzyme or microscopic changes despite a reduction of T lymphocyte infiltration in liver tissue. Similarly, co-administration of rituximab/everolimus with intrathecal dosing failed to block AAV-driven hepatotoxicity. Self-complementary AAV-induced acute liver injury appears to correlate with high hepatocellular vector load, macrophage activation, and type 1 interferon innate virus-sensing pathway responses. The current work characterizes key aspects pertaining to early AAV-driven hepatotoxicity in cynomolgus macaques, highlighting the usefulness of this nonclinical species in that context.

Neurofilament light chain and dorsal root ganglia injury after adeno-associated virus 9 gene therapy in nonhuman primates.

In nonhuman primates (NHPs), adeno-associated virus serotype 9 (AAV9) vectorized gene therapy can cause asymptomatic microscopic injury to dorsal root ganglia (DRG) and trigeminal ganglia (TG) somatosensory neurons, causing neurofilament light chain (NfL) to diffuse into cerebrospinal fluid (CSF) and blood. Data from 260 cynomolgus macaques administered vehicle or AAV9 vectors (intrathecally or intravenously) were analyzed to investigate NfL as a soluble biomarker for monitoring DRG/TG microscopic findings. The incidence of key DRG/TG findings with AAV9 vectors was 78% (maximum histopathology severity, moderate) at 2-12 weeks after the dose. When examined up to 52 weeks after the dose, the incidence was 42% (maximum histopathology severity, minimal). Terminal NfL concentrations in plasma, serum, and CSF correlated with microscopic severity. After 52 weeks, NfL returned to pre-dose baseline concentrations, correlating with microscopic findings of lesser incidence and/or severity compared with interim time points. Blood and CSF NfL concentrations correlated with asymptomatic DRG/TG injury, suggesting that monitoring serum and plasma concentrations is as useful for assessment as more invasive CSF sampling. Longitudinal assessment of NfL concentrations related to microscopic findings associated with AAV9 administration in NHPs indicates NfL could be a useful biomarker in nonclinical toxicity testing. Caution should be applied for any translation to humans.

Intrathecal sc-AAV9-CB-GFP: Systemic Distribution Predominates Following Single-Dose Administration in Cynomolgus Macaques.

Biodistribution of self-complementary adeno-associated virus-9 (scAAV9)-chicken ß-actin promoter-green fluorescent protein (GFP) was assessed in juvenile cynomolgus macaques infused intrathecally via lumbar puncture or the intracisterna magna (1.0×1013 or 3.0×1013 vg/animal), with necropsy 28 days later. Our results characterized central nervous system biodistribution compared with systemic organs/tissues by droplet digital polymerase chain reaction for DNA and in situ hybridization. Green fluorescent protein expression was characterized by Meso Scale Discovery electrochemiluminescence immunosorbent assay and immunohistochemistry (IHC). Biodistribution was widespread but variable, with vector DNA and GFP expression greatest in the spinal cord, dorsal root ganglia (DRG), and certain systemic tissues (e.g., liver), with low concentrations in many brain regions despite direct cerebrospinal fluid administration. Transduction and expression were observed primarily in perivascular astrocytes in the brain, with a paucity in neurons. Greater GFP expression was observed in hepatocytes, striated myocytes, cardiomyocytes, spinal cord lower motor neurons, and DRG sensory neurons by IHC. These results should be considered when evaluating scAAV9-based intrathecal delivery with the current expression cassette as a modality for neurologic diseases that require widespread brain neuronal expression. This capsid/expression cassette combination may be better suited for diseases that express a secreted protein and/or do not require widespread brain neuronal transduction.

Single-Dose Intrathecal Dorsal Root Ganglia Toxicity of Onasemnogene Abeparvovec in Cynomolgus Monkeys.

Intravenous onasemnogene abeparvovec is approved for the treatment of spinal muscular atrophy in children < 2 years. For later-onset patients, intrathecal onasemnogene abeparvovec may be advantageous over intravenous administration. Recently, microscopic dorsal root ganglion (DRG) changes were observed in nonhuman primates (NHPs) following intrathecal onasemnogene abeparvovec administration. To characterize these DRG findings, two NHP studies evaluating intrathecal onasemnogene abeparvovec administration were conducted: a 12-month study with a 6-week interim cohort and a 13-week study with a 2-week interim cohort. The latter investigated the potential impact of prednisolone or rituximab plus everolimus on DRG toxicity. An additional 6-month, single-dose, intravenous NHP study conducted in parallel evaluated onasemnogene abeparvovec safety (including DRG toxicity) with or without prednisolone coadministration. Intrathecal onasemnogene abeparvovec administration was well tolerated and not associated with clinical observations. Microscopic onasemnogene abeparvovec-related changes were observed in the DRG and trigeminal ganglion (TG) and included mononuclear cell inflammation and/or neuronal degeneration, which was colocalized with high vector transcript expression at 6 weeks postdose. Incidence and severity of DRG changes were generally decreased after 52 weeks compared with 6 weeks postdose. Other onasemnogene abeparvovec-related microscopic findings of axonal degeneration, mononuclear cell infiltrates and/or gliosis in the spinal cord, dorsal spinal nerve root/spinal nerves, and/or peripheral nerves were absent or found at decreased incidences and/or severities after 52 weeks. DRG and/or TG microscopic findings following intravenous onasemnogene abeparvovec dosing included minimal to slight neuronal degeneration and mononuclear cell inflammation at 6 weeks and 6 months postdose. Nervous system microscopic findings following intrathecal onasemnogene abeparvovec (≥1.2 × 1013 vg/animal) trended toward resolution after 52 weeks, supporting nonprogression of changes, including in the DRG. Onasemnogene abeparvovec-related DRG findings were not associated with electrophysiology changes and were not ameliorated by prednisolone or rituximab plus everolimus coadministration. The pathogenesis is possibly a consequence of increased vector genome transduction and/or transgene expression.

Discovery and Optimization of HKT288, a Cadherin-6-Targeting ADC for the Treatment of Ovarian and Renal Cancers.

Despite an improving therapeutic landscape, significant challenges remain in treating the majority of patients with advanced ovarian or renal cancer. We identified the cell-cell adhesion molecule cadherin-6 (CDH6) as a lineage gene having significant differential expression in ovarian and kidney cancers. HKT288 is an optimized CDH6-targeting DM4-based antibody-drug conjugate (ADC) developed for the treatment of these diseases. Our study provides mechanistic evidence supporting the importance of linker choice for optimal antitumor activity and highlights CDH6 as an antigen for biotherapeutic development. To more robustly predict patient benefit of targeting CDH6, we incorporate a population-based patient-derived xenograft (PDX) clinical trial (PCT) to capture the heterogeneity of response across an unselected cohort of 30 models-a novel preclinical approach in ADC development. HKT288 induces durable tumor regressions of ovarian and renal cancer models in vivo, including 40% of models on the PCT, and features a preclinical safety profile supportive of progression toward clinical evaluation.Significance: We identify CDH6 as a target for biotherapeutics development and demonstrate how an integrated pharmacology strategy that incorporates mechanistic pharmacodynamics and toxicology studies provides a rich dataset for optimizing the therapeutic format. We highlight how a population-based PDX clinical trial and retrospective biomarker analysis can provide correlates of activity and response to guide initial patient selection for first-in-human trials of HKT288. Cancer Discov; 7(9); 1030-45. ©2017 AACR.This article is highlighted in the In This Issue feature, p. 920.

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND) progress to date and future plans.

The INHAND Proposal (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) has been operational since 2005. A Global Editorial Steering Committee (GESC) manages the overall objectives of the project and the development of harmonized terminology for each organ system is the responsibility of the Organ Working Groups (OWG), drawing upon experts from North America, Europe and Japan.Great progress has been made with 9 systems published to date - Respiratory, Hepatobiliary, Urinary, Central/Peripheral Nervous Systems, Male Reproductive and Mammary, Zymbals, Clitoral and Preputial Glands in Toxicologic Pathology and the Integument and Soft Tissue and Female Reproductive System in the Journal of Toxicologic Pathology as supplements and on a web site - www.goreni.org. INHAND nomenclature guides offer diagnostic criteria and guidelines for recording lesions observed in rodent toxicity and carcinogenicity studies. The guides provide representative photo-micrographs of morphologic changes, information regarding pathogenesis, and key references. During 2012, INHAND GESC representatives attended meetings with representatives of the FDA Center for Drug Evaluation and Research (CDER), Clinical Data Interchange Standards Consortium (CDISC), and the National Cancer Institute (NCI) Enterprise Vocabulary Services (EVS) to begin incorporation of INHAND terminology as preferred terminology for SEND (Standard for Exchange of Nonclinical Data) submissions to the FDA. The interest in utilizing the INHAND nomenclature, based on input from industry and government toxicologists as well as information technology specialists, suggests that there will be wide acceptance of this nomenclature. The purpose of this publication is to provide an update on the progress of INHAND.