Anti-tumor activity and toxicokinetics analysis of MGAH22, an anti-HER2 monoclonal antibody with enhanced Fcγ receptor binding properties

Abstract

IntroductionResponse to trastuzumab in metastatic breast cancer correlates with expression of the high binding variant (158V) of the activating Fcγ receptor IIIA (CD16A). We engineered MGAH22, a chimeric anti-HER2 monoclonal antibody with specificity and affinity similar to trastuzumab, with an Fc domain engineered for increased binding to both alleles of human CD16A.MethodsMGAH22 was compared to an identical anti-HER2 mAb except for a wild type Fc domain. Antibody-dependent cell cytotoxicity (ADCC) assays were performed with HER2-expressing cancer cells as targets and human PBMC or purified NK cells as effectors. Xenograft studies were conducted in mice with wild type murine FcγRs; in mice lacking murine CD16; or in mice lacking murine CD16 but transgenic for human CD16A-158F, the low-binding variant. The latter model reproduces the differential binding between wild type and the Fc-optimized mAb for human CD16A. The JIMT-1 human breast tumor line, derived from a patient that progressed on trastuzumab therapy, was used in these studies. Single and repeat dose toxicology studies with MGAH22 administered intravenously at high dose were conducted in cynomolgus monkeys.ResultsThe optimized Fc domain confers enhanced ADCC against all HER2-positive tumor cells tested, including cells resistant to trastuzumab's anti-proliferative activity or expressing low HER2 levels. The greatest improvement occurs with effector cells isolated from donors homozygous or heterozygous for CD16A-158F, the low-binding allele. MGAH22 demonstrates increased activity against HER2-expressing tumors in mice transgenic for human CD16A-158F. In single and repeat-dose toxicology studies in cynomolgus monkeys, a species with a HER2 expression pattern comparable to that in humans and Fcγ receptors that exhibit enhanced binding to the optimized Fc domain, MGAH22 was well tolerated at all doses tested (15-150 mg/kg) and exhibited pharmacokinetic parameters similar to that of other anti-HER2 antibodies. Induction of cytokine release by MGAH22 in vivo or in vitro was similar to that induced by the corresponding wild type mAb or trastuzumab.ConclusionsThe data support the clinical development of MGAH22, which may have utility in patients with low HER2 expressing tumors or carrying the CD16A low-binding allele.

Preclinical Profile of the HER2-Targeting ADC SYD983/SYD985: Introduction of a New Duocarmycin-Based Linker-Drug Platform

“…A set of five human tumor cell lines were selected on the basis of their published HER2-status; breast carcinomas SK-BR-3 and BT-474 (both HER2 3þ), ovarian carcinoma SK-OV3 (HER2 2þ), and metastatic colon carcinoma SW-620 and lung adenocarcinoma NCI-H520 (both HER2 negative). The HER2 status of these cell lines was confirmed by quantifying HER2 levels using Qifikit, indicating 815,000 (SK-BR-3), 910,000 (BT-474), 600,000 (SK-OV3), 150 (NCI-H520), and 1100 (SW-620) HER2 molecules per cell which is in line with previous publications (21,22). First these cell lines were studied for their sensitivity to seco-DUBA 2 ( Fig.…”

Single-Domain Antibody–Based and Linker-Free Bispecific Antibodies Targeting FcγRIII Induce Potent Antitumor Activity without Recruiting Regulatory T Cells

“…Our in vitro data showed a strong and specific NK cell-mediated lysis of CEA-expressing tumor cells (from pancreatic and colorectal cancers) at picomolar concentrations, that is, orders of magnitude lower than conventional mAbs (10,42). These results suggest that a high affinity for FcgRIIIa translates into improved cytotoxic activity of effector cells in vitro, a finding also described with mutated and glycoengineered antibodies (43,44). As opposed to classical mAbs such as rituximab, target antigen density did not significantly impact bsFab-mediated ADCC as shown by the use of tumor cell lines expressing different amounts of CEA.…”

The “less-is-more” in therapeutic antibodies: Afucosylated anti-cancer antibodies with enhanced antibody-dependent cellular cytotoxicity

“…An Fc variant 18 with several mutations (F243L/R292P/Y300L/V305I/P396L) was identified and demonstrated about 100-fold enhanced ADCC activity 73 . MGAH22, from Macrogenics, is a chimeric IgG1 anti-HER2 antibody, with similar affinity and specificity to trastuzumab, containing the engineered Fc domain (variant 18) except that V305I was replaced with L235V to reduce FcγRIIb binding 74 . MGAH22 showed enhanced affinity to both FcγRIIIa variants (F158 and V158), but decreased affinity to inhibitory FcγRIIb 74 .…”

“…MGAH22, from Macrogenics, is a chimeric IgG1 anti-HER2 antibody, with similar affinity and specificity to trastuzumab, containing the engineered Fc domain (variant 18) except that V305I was replaced with L235V to reduce FcγRIIb binding 74 . MGAH22 showed enhanced affinity to both FcγRIIIa variants (F158 and V158), but decreased affinity to inhibitory FcγRIIb 74 . This translated into enhanced ADCC activity over the wild-type equivalent of MGAH22 antibody.…”

“…This translated into enhanced ADCC activity over the wild-type equivalent of MGAH22 antibody. In vivo , MGAH22 demonstrated enhanced anti-HER2 activity over HER2 positive tumor in transgenic mouse expressing the low affinity human FcγRIIIa F158 variant 74 . MGH22 is currently being evaluated in clinical studies of patients with HER2-positive cancers.…”