An Anti-B7-H4 Antibody–Drug Conjugate for the Treatment of Breast Cancer

Abstract

B7-H4 has been implicated in cancers of the female reproductive system and investigated for its possible use as a biomarker for cancer, but there are no preclinical studies to demonstrate that B7-H4 is a molecular target for therapeutic intervention of cancer. We provide evidence that the prevalence and expression levels of B7-H4 are high in different subtypes of breast cancer and that only a few normal tissues express B7-H4 on the cell membrane. These profiles of low normal expression and upregulation in cancer provide an opportunity for the use of antibody-drug conjugates (ADCs), cytotoxic drugs chemically linked to antibodies, for the treatment of B7-H4 positive cancers. We have developed an ADC specific to B7-H4 that uses a linker drug consisting of a potent antimitotic, monomethyl auristatin E (MMAE), linked to engineered cysteines (THIOMAB) via a protease labile linker. We will refer to ADCs that use the THIOMAB format as TDCs to help distinguish the format from standard MC-vc-MMAE ADCs that are conjugated to the interchain disulfide bonds. Anti-B7-H4 (h1D11)-MC-vc-PAB-MMAE (h1D11 TDC) produced durable tumor regression in cell line and patient-derived xenograft models of triple-negative breast cancer. It also binds rat B7-H4 with similar affinity to human and allowed us to test for target dependent toxicity in rats. We found that our anti-B7-H4 TDC has toxicity findings similar to untargeted TDC. Our results validate B7-H4 as an ADC target for breast cancer and support the possible use of this TDC in the treatment of B7-H4(+) breast cancer.

An Anti-GDNF Family Receptor Alpha 1 (GFRA1) Antibody–Drug Conjugate for the Treatment of Hormone Receptor–Positive Breast Cancer

“…Our IHC analysis further confirmed that RET is overexpressed with IHC score of 2þ/3þ only in 20% (6 of 29) patients, while 28% (8 of 29) patients showed IHC score 1þ and 52% (15 of 29) luminal A breast cancer patients showed no expression. B7H4 and Ly6E protein targets were also reported to be expressed in breast cancer tissues and both these targets showed IHC score of 2þ/3þ at 37% and 61% expression, respectively, in hormone receptorpositive breast cancer patients (23,24). On the basis of the protein expression criteria as described above, GFRA1 is therefore a potentially superior ADC target for the treatment of luminal A breast cancer.…”

Tumor Regression and Delayed Onset Toxicity Following B7-H4 CAR T Cell Therapy

“…We detected B7-H4 protein in the mammary gland, kidney, and in pancreatic islet cells, consistent with published reports. 19,37 We also detected previously uncharacterized B7-H4 expression in the esophagus, salivary gland, and liver. Positive staining was generally found in glandular epithelial cells of the salivary and breast, ductal epithelium of the liver, and in the tubular epithelium of the kidney.…”

“…Compounds such as anti-B7-H4 scFvs, 14 ADCC-mediating antibodies 43 and antibody drug conjugates 19 that cross react with murine B7-H4 have antitumor effects, but lack toxicity in mouse models. This may inherently be due to the differences in treatment modalities, as scFvs and antibodies are rapidly cleared, may not efficiently penetrate tissue, and lack the same potent effector functions as T cells.…”

“…[12][13][14][15] In normal murine and human tissue, B7-H4 messenger RNA is widely expressed in nonlymphoid tissues, 9,10,15-17 but evaluation of protein expression has been inconsistent across publications. 18 In 2015, Leong et al reported positive B7-H4 staining in the ductal epithelium of several normal tissues including the breast, pancreas, and kidney, 19 notably distinct from the primarily lymphoid distribution of PD-L1 and PD-L2 under noninflammatory conditions. 20 Additionally, use of an anti-B7-H4 antibodydrug conjugate did not result in toxicity in preclinical models, suggesting that B7-H4-targeted therapy could be applied safely.…”

An anti-CD3/anti–CLL-1 bispecific antibody for the treatment of acute myeloid leukemia

“…14 The lead antibody for CLL-1, and one of 3 anti-human CD3e molecules with different affinities to CD3e, as determined by Biacore (CD3eL [low, KD 5 50.0 nM], CD3eH [high, KD 5 0.5 nM], and CD3eVH [very high, KD 5 0.05 nM]), were assembled as a fulllength bispecific humanized IgG1 in a knob-and-hole format that faithfully resembles the native antibody structure. 15 To minimize antibody-mediated effector functions, mutations (C H 3 N297G) were introduced in the Fc domain to reduce interactions with Fcg receptors.…”