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Background: Monomethyl auristatin E (MMAE) has been used as a payload for several Food and Drug Administration (FDA) approved antibody-drug conjugates (ADCs). It is known that MMAE is released from the ADC following binding, internalisation and proteolytic degradation in target tissues. A striking discrepancy in systemic MMAE levels has been observed across species with 50-fold higher MMAE levels in human than that in rodents when normalised by ADC dose with unknown mechanism. Hypothesis and purpose: Multiple factors could affect systemic MMAE levels such as production and elimination of unconjugated MMAE following ADC dosing. In this study, we have explored whether MMAE displays differential red blood cell (RBC) partitioning across species that may contribute to the different MMAE levels seen between human and animals. Experiments: To determine MMAE RBC partitioning, tritium labelled MMAE ([3H]-MMAE) was incubated in whole blood from mice, rats, monkeys and humans in vitro, then RBC partitioning was determined and compared across species. To test whether MMAE released from the ADC would show any difference in RBC partitioning, pinatuzumab vedotin or polatuzumab vedotin was administered to mice, rats, and monkeys. MMAE levels were measured in both blood and plasma, and the ratios of MMAE levels were calculated as blood-to-plasma ratio (in vivo RBC partitioning). Results: Our in vitro data showed that unconjugated MMAE has a species-dependent RBC partitioning with strong RBC partitioning in mouse, rat, followed by monkey blood, whereas minimal RBC partitioning was seen in human blood. Incubation of 2 nM of MMAE in mouse blood resulted in a blood-to-plasma ratio of 11.8 ± 0.291, followed by rat, monkey, and human at 2.36 ± 0.0825, 1.57 ± 0.0250, and 0.976 ± 0.0620, respectively. MMAE RBC partitioning is also concentration-dependent, with an inverse relationship between RBC partitioning and MMAE concentration (higher RBC partitioning at lower concentration). In vivo dosing of pinatuzumab vedotin in mouse displayed systemic MMAE at about a 5-fold higher blood concentration compared to plasma concentration once MMAE reached a pseudo-equilibrium, while systemic MMAE from blood and plasma concentration showed a 1.65-fold difference in rat. Implication and conclusion: These data demonstrated that MMAE has a distinct RBC partitioning across different species, which may contribute to, at least in part, to the differential in the systemic MMAE levels observed in vivo between preclinical and clinical studies. These findings highlight the importance of fully characterising the ADME properties of both the ADC and its payload, to enable better translation from animals to human for ADC development. [ABSTRACT FROM AUTHOR]

Background: Polatuzumab vedotin, the first FDA-approved antibody-drug conjugate (ADC) targeting CD79b, is utilized in the treatment of previously untreated diffuse large B-cell lymphoma (DLBCL) or high-grade B-cell lymphoma (HGBL), as well as relapsed or refractory (R/R) DLBCL. Despite its approval, concerns persist regarding the long-term safety profile of polatuzumab vedotin. This study aims to evaluate the adverse events (AEs) associated with polatuzumab vedotin since its approval in 2019, utilizing data mining strategies applied to the FDA Adverse Event Reporting System (FAERS). Methods: Signal detection employed four methodologies, including reporting odds ratio (ROR), proportional reporting ratio (PRR), bayesian confidence propagation neural network (BCPNN), and multi-item gamma poisson shrinker (MGPS), to evaluate and quantify the signals of polatuzumab vedotin-associated AEs. Additionally, subgroup analyses based on patients age, gender, and fatal cases were conducted to investigate AEs occurrences in specific subpopulations. Results: A total of 1,521 reports listing polatuzumab vedotin as a "principal suspect (PS)" drug were collected from the FAERS database. Through concurrent compliance with four algorithms, 19 significant Standardized MedDRA Query (SMQ) AEs and 92 significant Preferred Term (PT) AEs were detected. Subgroup analyses revealed a higher incidence of PTs in male patients compared to female patients, increased likelihood of polatuzumab vedotin-associated AEs in elder patients (>65 years), and AEs with a high risk of fatal cases include: blood lactate dehydrogenase increased, cytopenia, and hydronephrosis. The median time to AEs occurrence following polatuzumab vedotin initiation was 18.5 (5-57.75) days, with 95% of AEs occurred within 162 days. Conclusion: This study identified various AEs associated with polatuzumab vedotin, offering critical insights for clinical monitoring and risk identification in patients receiving polatuzumab vedotin therapy. [ABSTRACT FROM AUTHOR]

Abstract Polatuzumab vedotin (Pola) is an approved therapy in combination with rituximab and bendamustine for relapsed or refractory diffuse large B‐cell lymphoma (RR‐DLBCL) based on positive results of the landmark phase II randomised G029365 trial. However, trial results for many approved novel therapies in RR‐DLBCL have not been replicated in routine care cohorts, as RR‐DLBCL patient populations are heterogeneous and trial eligibility is increasingly restrictive. We evaluated outcomes from pola ± bendamustine and rituximab in patients with RR‐DLBCL enrolled in a compassionate access program with no alternative treatment options identified via the Australasian Lymphoma and Related Diseases Registry according to their eligibility for the original phase II published study. Of 58 eligible patients, 74% met the criteria deeming them ineligible for the G029365 original study at the time of pola's commencement. Median progression‐free survival and overall survival in our cohort were 2.3 and 3.5 months, respectively. In contrast to the landmark trial cohort, more of our patients ceased therapy prior to completion, the majority due to progressive disease and only 8/58 received any subsequent treatment. Dismal outcomes in this Australian real‐world population demonstrate trial eligibility is challenging to meet, and newer treatments can be difficult to deliver in routine care. Clinically applicable results from therapeutic studies require trial cohorts to reflect representative clinical populations wherever possible, and more research is required to address the benefit of novel agents in the increasing majority who are ineligible for modern studies.

A novel antibody-drug conjugate (ADC), Polatuzumab vedotin has emerged as a promising player in the oncology field. This comprehensive review aims to elucidate the intricate details of Polatuzumab vedotin, encompassing its molecular structure, mechanisms of action, clinical applications, therapeutic efficacy, and ongoing research endeavors. With a focus on precision and targeted therapy, Polatuzumab vedotin stands as a beacon of hope in the battle against various malignancies. It has been regarded as a significant advancement in the field of targeted treatment of diffuse large B-cell lymphoma. As research continues to expand, our understanding of Polatuzumab vedotin, it is evident that its potential to improve patient outcomes and reduce the burden of cancer will remain a topic of great interest for the medical community.