Fc-engineered monoclonal antibodies to reduce off-target liver uptake.

BACKGROUND: Radiolabeled-antibodies usually display non-specific liver accumulation that may impair image analysis and antibody biodistribution. Here, we investigated whether Fc silencing influenced antibody biodistribution. We compared recombinant 89Zr-labeled antibodies (human IgG1 against different targets) with wild-type Fc and with mutated Fc (LALAPG triple mutation to prevent binding to Fc gamma receptors; FcγR). After antibody injection in mice harboring xenografts of different tumor cell lines or of immortalized human myoblasts, we analyzed antibody biodistribution by PET-CT and conventional biodistribution analysis. RESULTS: Accumulation in liver was strongly reduced and tumor-specific targeting was increased for the antibodies with mutated Fc compared with wild-type Fc. CONCLUSION: Antibodies with reduced binding to FcγR display lower liver accumulation and better tumor-to-liver ratios. These findings need to be taken into account to improve antibody-based theragnostic approaches.

Pharmacokinetic Variability Drives Palbociclib-Induced Neutropenia in Metastatic Breast Cancer Patients: Drug-Drug Interactions Are the Usual Suspects.

Palbociclib is a good candidate for therapeutic drug monitoring (TDM) due to its narrow therapeutic range and frequency of toxicities, particularly high-grade neutropenia. In this prospective, bicentric clinical trial, we evaluated the palbociclib exposure−toxicity relationship and determined the relevant sources of palbociclib pharmacokinetic variability, including drug−drug interactions (DDI). We followed 58 patients (mean age: 62.9 years) for 1 year. The geometric median of palbociclib plasma trough concentration (Ctrough) was 74.1 ng/mL. Neutropenia occurred in 70.7% of patients (high grade in 67.2% of patients). High-grade neutropenia occurrence during the first two palbociclib cycles was higher in patients with lower neutrophil count at initiation (p = 0.002). Palbociclib plasma Ctrough was correlated with high-grade neutropenia occurrence during the first two cycles (p = 0.024, OR 5.51). Co-treatment with agents that may interfere with palbociclib PK significantly influenced palbociclib Ctrough (p < 0.05). CYP3A4/P-glycoprotein inhibitors increased by 25% palbociclib Ctrough (p = 0.035), while antacids reduced it by 20% (p = 0.036). However, DDI did not have any significant effect on high-grade neutropenia occurrence (p > 0.05). This study confirms the major role of TDM to manage palbociclib safe use from the first week of treatment, particularly the significant incidence of hematological toxicity. Moreover, this first dedicated prospective study confirmed the importance of characterizing co-treatments to limit the DDI risk with oral-targeted therapies.

Therapeutic antibodies - natural and pathological barriers and strategies to overcome them.

Antibody-based therapeutics have become a major class of therapeutics with over 120 recombinant antibodies approved or under review in the EU or US. This therapeutic class has experienced a remarkable expansion with an expected acceleration in 2021-2022 due to the extraordinary global response to SARS-CoV2 pandemic and the public disclosure of over a hundred anti-SARS-CoV2 antibodies. Mainly delivered intravenously, alternative delivery routes have emerged to improve antibody therapeutic index and patient comfort. A major hurdle for antibody delivery and efficacy as well as the development of alternative administration routes, is to understand the different natural and pathological barriers that antibodies face as soon as they enter the body up to the moment they bind to their target antigen. In this review, we discuss the well-known and more under-investigated extracellular and cellular barriers faced by antibodies. We also discuss some of the strategies developed in the recent years to overcome these barriers and increase antibody delivery to its site of action. A better understanding of the biological barriers that antibodies have to face will allow the optimization of antibody delivery near its target. This opens the way to the development of improved therapy with less systemic side effects and increased patients' adherence to the treatment.

[Strategies of tumor-pecific targeting based on the antigenic tumor specificities and the tumor microenvironment characteristics]. / Stratégies de ciblage spécifique de la tumeur fondées sur les caractéristiques des antigènes tumoraux et du microenvironnement tumoral.

Monoclonal antibody (mAb)-based immunotherapy is booming in oncology. In 2020, more than 40% of FDA (Food and Drug Administration)-approved antibodies (34 out of 84 antibodies, according to The Antibody Society) have an indication for cancer therapy. In contrast to standard chemotherapy, they demonstrate a much better safety profile for patients. Despite this, adverse side effects may occur due to the targeting of the antigen also expressed by healthy tissues. For this reason, emerging strategies aim at optimizing the antibody format and considering the particularities of the tumor microenvironment to confer a more specific action of the antibody at the tumor site.

TITLE: Stratégies de ciblage spécifique de la tumeur fondées sur les caractéristiques des antigènes tumoraux et du microenvironnement tumoral. ABSTRACT: L'immunothérapie à base d'anticorps monoclonaux (AcM) connaît un plein essor en cancérologie. En 2020, plus de 40% des anticorps approuvés par la FDA (Food and Drug Administration) (34 sur 84 anticorps, selon The Antibody Society) ont une indication pour les thérapies anti-cancéreuses. Contrairement à la chimiothérapie standard, ils démontrent un bien meilleur profil de tolérance pour les patients. Malgré cela, des effets indésirables néfastes peuvent survenir en raison du ciblage de l'antigène qui est également exprimé au niveau des tissus sains. C'est pourquoi des stratégies émergentes visent à optimiser le format des anticorps et à tenir compte des particularités du microenvironnement tumoral pour conférer une action encore plus spécifique de l'anticorps au niveau tumoral.

Liquid chromatography-tandem mass spectrometric assay for the quantification of CDK4/6 inhibitors in human plasma in a clinical context of drug-drug interaction.

The CDK4/6 inhibitors palbociclib and ribociclib are kinase inhibitors used in association with hormonal therapy for the management of patients with metastatic breast cancer. Like most kinase inhibitors, therapeutic drug monitoring may be used for personalize their dosage. To this aim, we developed and validated a sensitive and specific HPLC-MS/MS method for palbociclib and ribociclib quantification in blood samples. We then quantified exposure to palbociclib (plasma trough concentration; Ctrough) in a real-life cohort of patients with locally invasive or metastatic breast cancer (n = 18) at day 15 of the first cycle of palbociclib treatment to characterize palbociclib concentration at steady state (Clinicaltrials.gov identifier NCT04025541, IdRCB n° 2018-A00064-51, 03/07/2018). The geometric mean (± standard deviation [min-max]) of palbociclib plasma Ctrough was 88.58 ng/mL (± 26.4 [46.5 ng/mL - 133 ng/mL]) at day 15. Some covariates, such as drug-drug interactions, could explain the concentration variations observed in our Caucasian cohort. These first results in real-life settings obtained with our HPLC-MS/MS method give important information on palbociclib monitoring and pharmacokinetic variability.