The receptor tyrosine kinase HER2 is overexpressed in approximately 20% of breast cancer, and its amplification is associated with reduced survival. Trastuzumab emtansine (Kadcyla, T-DM1), an antibody-drug conjugate that is comprised of trastuzumab covalently linked to the antimitotic agent DM1 through a stable linker, was designed to selectively deliver DM1 to HER2-overexpressing tumor cells. T-DM1 is approved for the treatment of patients with HER2-positive metastatic breast cancer following progression on trastuzumab and a taxane. Despite the improvement in clinical outcome, many patients who initially respond to T-DM1 treatment eventually develop progressive disease. The mechanisms that contribute to T-DM1 resistance are not fully understood. To this end, we developed T-DM1-resistant models to examine the mechanisms of acquired T-DM1 resistance. We demonstrate that decreased HER2 and upregulation of MDR1 contribute to T-DM1 resistance in KPL-4 T-DM1-resistant cells. In contrast, both loss of SLC46A3 and PTEN deficiency play a role in conferring resistance in BT-474M1 T-DM1-resistant cells. Our data suggest that these two cell lines acquire resistance through distinct mechanisms. Furthermore, we show that the KPL-4 T-DM1 resistance can be overcome by treatment with an inhibitor of MDR1, whereas a PI3K inhibitor can rescue PTEN loss-induced resistance in T-DM1-resistant BT-474M1 cells. Our results provide a rationale for developing therapeutic strategies to enhance T-DM1 clinical efficacy by combining T-DM1 and other inhibitors that target signaling transduction or resistance pathways..

The pharmacokinetic (PK) behavior of monoclonal antibodies in cynomolgus monkeys (cynos) is generally translatable to that in humans. Unfortunately, about 39% of the antibodies evaluated for PKs in cynos have fast nonspecific (or non-targetmediated) clearance (in-house data). An empirical model relating variable region (Fv) charge and hydrophobicity to cyno nonspecific clearance was developed to gauge the risk an antibody would have for fast nonspecific clearance in the monkey. The purpose of this study was to evaluate the predictability of this empirical model on cyno nonspecific clearance with antibodies specifically engineered to have either high or low Fv charge. These amino acid changes were made in the Fv region of two test antibodies, humAb4D5-8 and anti-lymphotoxin ␣. The humAb4D5-8 has a typical nonspecific clearance in cynos, and by making it more positively charged, the antibody acquires fast nonspecific clearance, and making it less positively charged did not impact its clearance. Anti-lymphotoxin ␣ has fast nonspecific clearance in cynos, and making it more positively charged caused it to clear even faster, whereas making it less positively charged caused it to clear slower and within the typical range. These trends in clearance were also observed in two other preclinical species, mice and rats. The effect of modifying Fv charge on subcutaneous bioavailability was also examined, and in general bioavailability was inversely related to the direction of the Fv charge change. Thus, modifying Fv charge appears to impact antibody PKs, and the changes tended to correlate with those predicted by the empirical model.Hundreds of monoclonal antibody (mAb) therapeutics have been evaluated in clinical trials as potential life-saving therapeutics, yet only about 30 are approved for use in the United States and/or Europe, and they span therapeutic areas such as oncology, ophthalmology, viral infections, and autoimmune disease (1). These therapeutics fail for four main reasons, including lack of efficacy, safety, business, and others (2). As such, there is an effort to conduct appropriate preclinical studies to reduce the chances of failure as much as possible in the clinic. The focus of this paper is on efforts to lower the risk of fast antibody pharmacokinetics.Factors that affect antibody pharmacokinetics (PK) 2 include antibody-specific properties (charge, hydrophobicity, target affinity, FcRn affinity, Fc␥ receptor interactions, and glycosylation) (3), target properties (expression level, turnover rate, and soluble versus membrane-associated) (4, 5), drug administration (dose and route) (3, 6), anti-therapeutic antibody formation (6, 7), off-target/nonspecific binding (8 -12), and disease state (healthy volunteers versus patients) (13). Given the many factors that could affect the PK of therapeutic antibodies, finding a representative preclinical species in which to assess PK is imperative. An in-depth analysis of 23 monoclonal antibodies with linear PK and six with non-linear PK from three preclinical species...

Tau has become an attractive alternative target for passive immunotherapy efforts for Alzheimer’s disease (AD). The anatomical distribution and extent of tau pathology correlate with disease course and severity better than other disease markers to date. We describe here the generation, preclinical characterization, and phase 1 clinical characterization of semorinemab, a humanized anti-tau monoclonal antibody with an immunoglobulin G4 (igG4) isotype backbone. Semorinemab binds all six human tau isoforms and protects neurons against tau oligomer neurotoxicity in cocultures of neurons and microglia. In addition, when administered intraperitoneally once weekly for 13 weeks, murine versions of semorinemab reduced the accumulation of tau pathology in a transgenic mouse model of tauopathy, independent of antibody effector function status. Semorinemab also showed clear evidence of target engagement in vivo, with increases in systemic tau concentrations observed in tau transgenic mice, nonhuman primates, and humans. Higher concentrations of systemic tau were observed after dosing in AD participants compared to healthy control participants. No concerning safety signals were observed in the phase 1 clinical trial at single doses up to 16,800 mg and multiple doses totaling 33,600 mg in a month.

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Background and Purpose The potential for therapeutic antibody treatment of neurological diseases is limited by poor penetration across the blood–brain barrier. I.c.v. delivery is a promising route to the brain; however, it is unclear how efficiently antibodies delivered i.c.v. penetrate the cerebrospinal spinal fluid (CSF)‐brain barrier and distribute throughout the brain parenchyma. Experimental Approach We evaluated the pharmacokinetics and pharmacodynamics of an inhibitory monoclonal antibody against β‐secretase 1 (anti‐BACE1) following continuous infusion into the left lateral ventricle of healthy adult cynomolgus monkeys. Key Results Animals infused with anti‐BACE1 i.c.v. showed a robust and sustained reduction (~70%) of CSF amyloid‐β (Aβ) peptides. Antibody distribution was near uniform across the brain parenchyma, ranging from 20 to 40 nM, resulting in a ~50% reduction of Aβ in the cortical parenchyma. In contrast, animals administered anti‐BACE1 i.v. showed no significant change in CSF or cortical Aβ levels and had a low (~0.6 nM) antibody concentration in the brain. Conclusion and Implications I.c.v. administration of anti‐BACE1 resulted in enhanced BACE1 target engagement and inhibition, with a corresponding dramatic reduction in CNS Aβ concentrations, due to enhanced brain exposure to antibody.