A Phase 1a Study to Evaluate Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of RO7303509, an Anti-TGFβ3 Antibody, in Healthy Volunteers

INTRODUCTION

Transforming growth factor beta (TGFβ) cytokines (TGFβ1, TGFβ2, and TGFβ3) play critical roles in tissue fibrosis. However, treatment with systemic pan-TGFβ inhibitors have demonstrated unacceptable toxicities. In this study, we evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of RO7303509, a high-affinity, TGFβ3-specific, humanized immunoglobulin G1 monoclonal antibody, in healthy adult volunteers (HVs).

METHODS

This phase 1a, randomized, double-blind trial included six cohorts for evaluation, with each cohort receiving single doses of placebo or RO7303509, administered intravenously (IV; 50 mg, 150 mg, 240 mg) or subcutaneously (SC; 240 mg, 675 mg, 1200 mg). The frequency and severity of adverse events (AEs) and RO7303509 serum concentrations were monitored throughout the study. We also measured serum periostin and cartilage oligomeric matrix protein (COMP) by immunoassay and developed a population pharmacokinetics model to characterize RO7303509 serum concentrations.

RESULTS

The study enrolled 49 HVs, with a median age of 39 (range 18-73) years. Ten (27.8%) RO7303509-treated subjects reported 24 AEs, and six (30.8%) placebo-treated subjects reported six AEs. The most frequent AEs related to the study drug were injection site reactions and infusion-related reactions. Maximum serum concentrations (Cmax) and area under the concentration-time curve from time 0 to infinity (AUC0-inf) values for RO7303509 appeared to increase dose-proportionally across all doses tested. Serum concentrations across cohorts were best characterized by a two-compartment model plus a depot compartment with first-order SC absorption kinetics. No subjects tested positive for anti-drug antibodies (ADAs) at baseline; one subject (2.8%; 50 mg IV) tested positive for ADAs at a single time point (day 15). No clear pharmacodynamic effects were observed for periostin or COMP upon TGFβ3 inhibition.

CONCLUSION

RO7303509 was well tolerated at single SC doses up to 1200 mg in HVs with favorable pharmacokinetic data that appeared to increase dose-proportionally. TGFβ3-specific inhibition may be suitable for development as a chronic antifibrotic therapy.

TRIAL REGISTRATION

ISRCTN13175485.

The HER2-directed antibody-drug conjugate DHES0815A in advanced and/or metastatic breast cancer: preclinical characterization and phase 1 trial results

Approved antibody-drug conjugates (ADCs) for HER2-positive breast cancer include trastuzumab emtansine and trastuzumab deruxtecan. To develop a differentiated HER2 ADC, we chose an antibody that does not compete with trastuzumab or pertuzumab for binding, conjugated to a reduced potency PBD (pyrrolobenzodiazepine) dimer payload. PBDs are potent cytotoxic agents that alkylate and cross-link DNA. In our study, the PBD dimer is modified to alkylate, but not cross-link DNA. This HER2 ADC, DHES0815A, demonstrates in vivo efficacy in models of HER2-positive and HER2-low cancers and is well-tolerated in cynomolgus monkey safety studies. Mechanisms of action include induction of DNA damage and apoptosis, activity in non-dividing cells, and bystander activity. A dose-escalation study (ClinicalTrials.gov: NCT03451162) in patients with HER2-positive metastatic breast cancer, with the primary objective of evaluating the safety and tolerability of DHES0815A and secondary objectives of characterizing the pharmacokinetics, objective response rate, duration of response, and formation of anti-DHES0815A antibodies, is reported herein. Despite early signs of anti-tumor activity, patients at higher doses develop persistent, non-resolvable dermal, ocular, and pulmonary toxicities, which led to early termination of the phase 1 trial.

Abstract P2-13-25: A phase I dose-escalation study of DHES0815A, a HER2-targeting antibody-drug conjugate with a DNA monoalkylator payload, in patients with HER2-positive breast cancer

Background: Despite the success of multiple HER2-targeted agents in HER2+ breast cancer (BC), resistance remains a challenge and novel therapies are needed. DHES0815A is a THIOMABTM antibody-drug conjugate consisting of a humanized IgG1 anti-HER2 monoclonal antibody (mAb) conjugated to the DNA alkylating agent PBD-MA. The reduced potency of PBD-MA compared to PBD dimers and the stability of the conjugation site and linker were designed to improve tolerability, whereas the binding of the mAb to a HER2 epitope distinct from trastuzumab and pertuzumab was designed to enable combination therapy with existing HER2 therapies. Methods: This first-in-human, Phase I, open-label, multicenter, dose escalation study used a 3+3 dose escalation design to assess the safety, pharmacokinetics (PK), and preliminary anti-tumor activity of DHES0815A in patients with metastatic HER2-positive BC refractory to established therapies (NCT03451162). DHES0815A (0.6-6.0 mg/kg) was administered intravenously every 3 weeks (Q3W) until intolerable toxicity or disease progression. Results: A total of 14 patients were treated with DHES0815A; all had ≥3 prior lines of therapy. Thirteen patients discontinued treatment due to progressive disease (43%), adverse events (AE; [29%]) symptomatic deterioration (14%) or other (7%); 1 patient remains on treatment. DHES0815A was initially well-tolerated for doses up to 2.4 mg/kg. At 4.0 mg/kg and 6.0 mg/kg, the first dose was also well-tolerated with no dose limiting toxicities, however, following 3 or more cycles at 4.0 mg/kg or 2 or more cycles at 6.0 mg/kg, safety events involving skin, eyes, and lung emerged. Skin events were reported in 50% of patients (all doses) and related events occurring in n≥2 patients included pruritus (36%), rash (36%), and skin hyperpigmentation (21%). Ocular toxicities were reported in 57% and related events occurring in n≥2 patients included photophobia (21%), conjunctivitis, eye pain, and dry eye (each 14%). Lung toxicities were reported in 36% of patients; events occurring in n≥2 included pneumonitis (14%). Other related skin, ocular, and pulmonary events occurring in 1 patient (7%) included palmar-plantar erythrodysaesthesia, macular rash, blurred vision, eyelid edema, periorbital edema, blepharitis, punctate keratitis, wheezing, allergic rhinitis, and pneumothorax. Most events were grade 1 or 2 although 3 patients experienced grade 3 ocular events (blepharitis, eye pain, photophobia). Due to these AEs, DHES0815A dose was decreased to 2.4 mg/kg Q3W for all enrolled patients and accrual was stopped. All 5 patients receiving doses of 4.0 mg/kg and 6.0 mg/kg discontinued due to AEs. At lower doses, 1 patient receiving 2.4 mg/kg developed grade 2 rash at Cycle 21 and 1 patient receiving 1.2 mg/kg developed grade 1 rash, pruritis, and skin hyperpigmentation between Cycles 28-30. Nonlinear PK of antibody-conjugated PBD-MA (acPBD-MA) was observed due to target mediated drug disposition at 0.6, 1.2, and 2.4 mg/kg; PK approached linear at 4.0 mg/kg. Minimal systemic exposure of unconjugated PBD-MA was observed. Overall, 1 patient (7%) in the 1.2 mg/kg cohort achieved a confirmed complete response. As of 10Jun21, this patient remains on study after more than 32 months on treatment. Ten patients (86%) showed a confirmed best overall response of stable disease (86%). Conclusion: Despite some anti-tumor activity observed with DHES0815A, development in HER2-positive BC has been discontinued due to safety concerns and the narrow therapeutic window. Toxicities observed in skin, lung, and eyes are clinically apparent only after repeated dose administration. If future exploration of PBD-MA-based constructs is performed in the clinic, close monitoring for delayed toxicities is warranted.

Citation Format: Ian Krop, Erika Hamilton, Kyung Hae Jung, Shanu Modi, Kevin M Kalinsky, Gail Phillips, Rong Shi, Sharareh Monemi, Michael Mamounas, Ola Saad, Voleak Choeurng, Renee Commerford, Eunpi Cho, Alexander Ungewickell, Patricia LoRusso. A phase I dose-escalation study of DHES0815A, a HER2-targeting antibody-drug conjugate with a DNA monoalkylator payload, in patients with HER2-positive breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-25.

A phase Ib trial of belvarafenib in combination with cobimetinib in patients with advanced solid tumors: Interim results of dose-escalation and patients with NRAS-mutant melanoma of dose-expansion

3007

Background: Belvarafenib, a potent, selective RAF dimer (type II) inhibitor, exhibits clinical activity in BRAFV600E- and NRAS-mutant (NRASm) melanoma patients. The combination of belvarafenib and cobimetinib more potently and durably suppressed MAPK pathway output and tumor growth than currently approved BRAF/MEK inhibitors in RAS- or RAF-mutant tumor xenograft models. This interim results of phase 1b trial evaluated the safety, tolerability, pharmacokinetics, and anti-tumor activity of belvarafenib in combination with cobimetinib in dose-escalation and NRASm melanoma patients among the 9 indication-specific expansion cohorts. Methods: Patients with locally advanced or metastatic solid tumors harboring RAS or RAF mutation were enrolled in the dose-escalation stage, and the recommended doses were explored in the indication-specific expansion stage. Patients in the dose-escalation stage were given belvarafenib (100–300mg BID) in combination with cobimetinib (20–40mg QD) and the dose of subsequent cohorts was decided by a traditional 3+3 design and safety profile. Primary objectives were to evaluate the safety and tolerability, to estimate the maximum tolerable dose, and to identify the RP2D of the combination. Results: A total of 32 patients enrolled were evaluated for safety analysis; 19 were enrolled in 4 cohorts in the dose-escalation stage and 13 NRASm melanoma patients were enrolled in the indication-specific expansion stage (cut-off date: 2020-7-24). There were 3 DLTs (G3 colitis, G3 diarrhoea, G3 nausea) in 2 patients at the starting dose of belvarafenib 200mg BID continuously and cobimetinib 40mg QD 21/7 schedule. Belvarafenib dose was escalated to 300mg BID with cobimetinib 20mg QD, which did not result in DLTs. The most common treatment-emergent adverse events that occurred in ≥30% of 32 patients were dermatitis acneiform, diarrhoea, constipation, and increase in blood creatine phosphokinase. Two combination doses were explored in the indication-specific expansion stage. Out of the 9 indication-specific expansion cohorts, NRASm melanoma patients exhibited promising efficacy signal; 5 patients reached partial responses (PRs) out of 13, giving a response rate of 38.5%. Among them, 11 had been previously treated with checkpoint inhibitors (CPIs), including 5 (45.5%) who achieved PR. The median PFS was 7.3 months and 5 patients remained on the treatment at the cut-off date. Conclusions: Belvarafenib in combination with cobimetinib showed acceptable tolerability and encouraging efficacy in NRASm melanoma, and in those with prior CPI treatment. Further research is ongoing in other cohorts (Clinicaltrial.gov, NCT03284502) and in NRASm melanoma (reference GO42273 by clinicaltrials.gov ID number). *S.J.S and J.L contributed equally to this work. Clinical trial information: NCT03284502.

A phase Ib study to evaluate the oral selective estrogen receptor degrader GDC-9545 alone or combined with palbociclib in metastatic ER-positive HER2-negative breast cancer

1023

Background: GDC-9545 is a potent, orally available, selective estrogen receptor degrader developed for the treatment of ER-positive (ER+) breast cancer alone or combined with CDK4/6 inhibitors. A first-in-human study evaluated 10-250 mg GDC-9545; tolerability, pharmacokinetic (PK), pharmacodynamic (PD), and clinical results support expansion cohorts at ≥30 mg (Jhaveri et al., 2019). Methods: This study evaluated PK, PD, and efficacy of GDC-9545 alone and combined with palbociclib, ± LHRH agonist. Eligible patients (pts) had ER+ (HER2-) metastatic breast cancer (MBC) with ≤ 2 prior therapies in the advanced or metastatic setting. No prior treatment with CDK4/6 inhibitor was allowed in pts receiving palbociclib. Results: Eight-five pts were enrolled in 2 cohorts: GDC-9545 100 mg given once daily ± LHRH agonist (Cohort A), and GDC-9545 100 mg +125 mg palbociclib on a 21 day on/7 day off schedule ± LHRH agonist (Cohort B). Of the 39 pts in Cohort A, adverse events (AE) occurring in ≥10% of pts were fatigue, cough, back pain, pain in extremity, and arthralgia. Related AEs were generally Grade (G) 1-2; there were 3 related G3 AEs of fatigue, transaminase increased, and diarrhea. Two pts had GDC-9545 reduced, one due to G3 diarrhea and another due to G3 transaminitis. Of the 46 pts in Cohort B, AEs in ≥10% of pts were neutropenia, fatigue, bradycardia, diarrhea, constipation, dizziness, nausea, anemia, asthenia, thrombocytopenia, pruritus, and visual impairment. Twenty-six (57%) pts had G≥3 AEs. G≥3 neutropenia was reported in 23 (50%) pts. One pt had palbociclib reduced due to G3 febrile neutropenia. Eleven (13%) of 85 pts had G1 asymptomatic bradycardia considered related to GDC-9545. No pts in either cohort discontinued study treatment due to AEs. PK analysis and clinical data demonstrate no clinically relevant drug-drug interactions between GDC-9545 and palbociclib. Reduced ER, PR, and Ki67 levels, and an ER activity signature, were observed in paired pre- and on-treatment biopsies (n = 12). Eighteen of 33 pts in Cohort A had either confirmed partial responses or were on study 24 weeks (clinical benefit rate 55%). Clinical benefit was observed in pts with prior fulvestrant treatment and with detectable ESR1 mutations at enrollment. Clinical benefit data for both cohorts are anticipated to be mature in April 2020. Conclusions: GDC-9545 was well-tolerated as a single agent and in combination with palbociclib with encouraging PK, PD, and anti-tumor activity in ER+ MBC to support Phase III development. Clinical trial information: NCT03332797 .

The role of the WDR36 gene on chromosome 5q22.1 in a large family with primary open-angle glaucoma mapped to this region

OBJECTIVE

To determine whether mutations in the WD40-repeat 36 (WDR36) gene are responsible for primary open-angle glaucoma (POAG) that maps to the GLC1G locus in a family with 16 affected family members.

METHODS

Ninety-two family members underwent clinical evaluation for POAG on the basis of intraocular pressures, cupping of discs, and visual fields after informed consent was obtained. All 23 exons of WDR36 were sequenced in DNA from 5 affected and 2 unaffected family members.

RESULTS

Sixteen family members showed evidence of POAG. A number of sequence variations were identified in family members; most of the variations were previously described single-nucleotide polymorphisms also present in the general population. The 3 new sequence changes were all intronic; 2 were found in only 1 of the family members undergoing screening.

CONCLUSIONS

Several polymorphisms, including known single-nucleotide polymorphisms, were identified; however, none of these were consistent with disease-causing mutations. A mutation in a noncoding region of WDR36 may be responsible for POAG in this family, or another gene in this region may be the actual cause of glaucoma in this family.

CLINICAL RELEVANCE

The finding that the WDR36 gene is probably not the responsible gene in this family further documents the genetic heterogeneity of POAG.

Identification of a novel adult-onset primary open-angle glaucoma (POAG) gene on 5q22.1

Glaucoma is a leading cause of blindness in virtually every country. Development of an accurate diagnostic test for presymptomatic detection of individuals at risk is an urgent requisition for this condition. Herein, we report mapping of a new adult-onset primary open-angle glaucoma (POAG) locus on 5q22.1 (GLC1G) and identification of its defective gene. Mutation screening of seven candidate genes from the GLC1G critical region (approximately 2 Mb between D5S1466 and D5S2051) identified only one significant alteration in the WDR36 (WD40-repeat 36) gene. This mutation (i.e. D658G) was segregated in all affected members of our first GLC1G-linked family but it was absent in 476 normal control chromosomes. Further screening of WDR36 in a total of 130 POAG families revealed 24 DNA variations. Overall, four mutations (N355S, A449T, R529Q and D658G) were identified in 17 (5.02-6.92%) unrelated POAG subjects, 11 with high-pressure and six with low-pressure glaucoma. These mutations were absent in a minimum of 200 normal control chromosomes and, further they were conserved between WDR36 orthologues in mouse, rat, dog, chimp and human. WDR36 is a novel gene with 23 exons, which encodes for 951 amino acids and a protein with multiple G-beta WD40 repeats. By northern blotting, two distinct mRNA transcripts of 5.9 and 2.5 kb were observed in human heart, placenta, liver, skeletal muscle, kidney and pancreas. WDR36 gene expression in lens, iris, sclera, ciliary muscles, ciliary body, trabecular meshwork, retina and optic nerve were established by RT-PCR. In mouse, two transcripts of 3.5 and 2.9 kb showed analogous expression patterns to human. mRNA expressions were detected in 7-, 11-, 15- and 17-day-old developing mouse embryos. In summary, WDR36 is a novel causative gene for adult-onset POAG at the GLC1G locus. Specific ocular expressions and observed mutations are consistent with WDR36 role in etiology of both high- and low-pressure glaucoma.