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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]

Aims: This study aims to develop a generalized pharmacokinetic (PK) model for monomethyl auristatin E (MMAE)‐based antibody–drug conjugates (ADCs) that can simultaneously capture the PK of multiple ADC analytes commonly measured in the clinic. Methods: A comprehensive literature review was conducted to collect PK data on MMAE‐based ADCs from clinical trials. From each study, PK profiles of total antibody, the ADC, conjugated MMAE, and unconjugated MMAE, were extracted. These data were pooled and dose‐normalized to evaluate the generalizability of PK across various ADCs and dose levels. Upon confirming PK generalizability, a generalized PK model for MMAE‐based ADCs was developed using the entire dataset. Furthermore, exposure metrics (Cmax and AUC) reported across the range of doses were combined to establish linear relationships between dose and exposure metrics for MMAE‐based ADCs. Results: A total of 109 PK profiles from 18 distinct MMAE‐based ADCs were gathered. The dose‐normalized PK profiles supported the generalizability of PK for MMAE‐based ADCs. A generalized PK model was developed, which enabled capturing the PK data for 4 ADC analytes across all collected MMAE‐based ADCs. A linear relationship between dose and PK exposure metrics was established, enabling the prediction of typical exposure values across different doses for MMAE‐based ADCs. Conclusions: This study comprehensively analysed clinical PK data from different valine–citrulline (vc)‐MMAE‐based ADCs. The generalized PK model developed here serves as an important tool for a priori prediction of the PK for multiple ADC analytes in clinical settings and lays the foundation for establishing generalized exposure–response and exposure–toxicity correlations for MMAE‐based ADCs. [ABSTRACT FROM AUTHOR]

Prostate stem cell antigen (PSCA) is expressed in all stages of prostate cancer, including in advanced androgen-independent tumors and bone metastasis. PSCA may associate with prostate carcinogenesis and lineage plasticity in prostate cancer. PSCA is also a promising theranostic marker for a variety of other solid tumors, including pancreatic adenocarcinoma and renal cell carcinoma. Here, we identified a novel fully human PSCA antibody using phage display methodology. The structure-based affinity maturation yielded a high-affinity binder, F12, which is highly specific and does not bind to 6,000 human membrane proteins based on a membrane proteome array assay. F12 targets PSCA amino acids 63–69 as tested by the peptide scanning microarray, and it cross-reacts with the murine PSCA. IgG1 F12 efficiently internalizes into PSCA-expressing tumor cells. The antimitotic reagent monomethyl auristatin E (MMAE)-conjugated IgG1 F12 (ADC, F12-MMAE) exhibits dose-dependent efficacy and specificity in a human prostate cancer PC-3-PSCA xenograft NSG mouse model. This is a first reported ADC based on a fully human PSCA antibody and MMAE that is characterized in a xenograft murine model, which warrants further optimizations and investigations in additional preclinical tumor models, including prostate and other solid tumors.

Monomethyl auristatin E (MMAE) is a derivative of the marine peptide Dolastatin 10, which has therapeutic effects against various cancers according to its antimitotic activity in multiple clinical trials. The antibody drug conjugate (ADC) of MMAE is currently used in clinical practice. However, the safety issues of MMAE-based ADC, such as high drug toxicity and poor bioavailability, still exist when using it for anticancer therapy. A sustained release of drug delivery approach should be used to reduce toxicity and achieve sufficient anticancer effects. Herein, PLGA-b-PEG 2 0 0 0 with excellent biocompatibility and slow degradation ability was adopted to construct MMAE-loaded nanoparticles for safe and effective chemotherapy. The sustained release effect and the immunogenic cell death (ICD) effect of PLGA-MMAE nanoparticles were assessed by in vitro experiments. The PLGA-MMAE nanoparticles effectively accumulated in the tumor through the enhanced permeability and retention (EPR) effect, inducing cell apoptosis and causing a certain degree of immune response. The sustained drug release of PLGA-MMAE improved the bioavailability and effectively reduced the toxicity and development of the tumor compared to the effect of free MMAE or ADC. Overall, this study provides a safe and effective chemotherapeutic approach, as well as a simple and effective synthetic process for MMAE-based nanoparticles, improving their therapeutic efficacy and safety. [ABSTRACT FROM AUTHOR]

Abstract Malignant pleural mesothelioma (MPM) is a malignant tumor of the pulmonary pleural tissue for which there is a lack of effective targeted therapy. In this study, moderate to high V‐domain immunoglobulin T‐cell activation suppressor (VISTA) expression levels were observed in most MPM clinical tumor samples. We prepared two high‐affinity anti‐VISTA monoclonal antibodies (mAbs) and generated two novel VISTA‐targeted antibody‐drug conjugates (ADCs) by conjugating anti‐VISTA mAbs with the potent cytotoxic drug monomethyl auristatin E (MMAE). αV1‐MMAE and αV2‐MMAE showed potent killing effects to VISTA‐positive cell lines in vitro, with half‐maximal inhibitory concentration (IC50) of nanomolar levels. αV1‐MMAE and αV2‐MMAE were also able to significantly induce apoptosis and cause G2/M phase arrest in VISTA‐positive cells. In the VISTA‐positive human MPM xenograft model, both αV1‐MMAE and αV2‐MMAE showed significant antitumor activity, led to a significant survival advantage compared to mice in the control group, and effectively induced apoptosis in the tumor tissues of mice. In conclusion, we demonstrated that the novel VISTA‐targeted ADCs (αV1‐MMAE and αV2‐MMAE), especially αV1‐MMAE, had potent killing effects against VISTA‐positive MPM cells both in vitro and in vivo. Therefore, through further development, they may have the potential to become new drugs for the treatment of MPM.

Glioblastoma is the deadliest form of brain tumor. The presence of the blood–brain barrier (BBB) significantly hinders chemotherapy, necessitating the development of innovative treatment options for this tumor. This report presents the in vitro and in vivo efficacy of an antibody–drug conjugate (ADC) that targets glypican-1 (GPC1) in glioblastoma. The GPC1-ADC was created by conjugating a humanized anti-GPC1 antibody (clone T2) with monomethyl auristatin E (MMAE) via maleimidocaproyl-valine-citrulline-p-aminobenzyloxycarbonyl linkers. Immunohistochemical staining analysis of a glioblastoma tissue microarray revealed that GPC1 expression was elevated in more than half of the cases. GPC1-ADC, when bound to GPC1, was efficiently and rapidly internalized in glioblastoma cell lines. It inhibited the growth of GPC1-positive glioma cell lines by inducing cell cycle arrest in the G2/M phase and triggering apoptosis in vitro. We established a heterotopic xenograft model by subcutaneously implanting KALS-1 and administered GPC1-ADC intravenously. GPC1-ADC significantly inhibited tumor growth and increased the number of mitotic cells. We also established an orthotopic xenograft model by intracranially implanting luciferase-transfected KS-1-Luc#19. After injecting Evans blue and resecting brain tissues, dye leakage was observed in the implantation area, confirming BBB disruption. We administered GPC1-ADC intravenously and measured the luciferase activity using an in vivo imaging system. GPC1-ADC significantly inhibited tumor growth and extended survival. In conclusion, GPC1-ADC demonstrated potent intracranial activity against GPC1-positive glioblastoma in an orthotopic xenograft model. These results indicate that GPC1-ADC could represent a groundbreaking new therapy for treating glioblastoma beyond the BBB.

Monomethyl auristatin E (MMAE) is a derivative of the marine peptide Dolastatin 10, which has therapeutic effects against various cancers according to its antimitotic activity in multiple clinical trials. The antibody drug conjugate (ADC) of MMAE is currently used in clinical practice. However, the safety issues of MMAE-based ADC, such as high drug toxicity and poor bioavailability, still exist when using it for anticancer therapy. A sustained release of drug delivery approach should be used to reduce toxicity and achieve sufficient anticancer effects. Herein, PLGA-b-PEG[Formula: see text] with excellent biocompatibility and slow degradation ability was adopted to construct MMAE-loaded nanoparticles for safe and effective chemotherapy. The sustained release effect and the immunogenic cell death (ICD) effect of PLGA-MMAE nanoparticles were assessed by in vitro experiments. The PLGA-MMAE nanoparticles effectively accumulated in the tumor through the enhanced permeability and retention (EPR) effect, inducing cell apoptosis and causing a certain degree of immune response. The sustained drug release of PLGA-MMAE improved the bioavailability and effectively reduced the toxicity and development of the tumor compared to the effect of free MMAE or ADC. Overall, this study provides a safe and effective chemotherapeutic approach, as well as a simple and effective synthetic process for MMAE-based nanoparticles, improving their therapeutic efficacy and safety.

Antibody-Drug Conjugates (ADCs) and Small Molecule-Drug Conjugates (SMDCs) represent successful examples of targeted drug-delivery technologies for overcoming unwanted side effects of conventional chemotherapy in cancer treatment. In both strategies, a cytotoxic payload is connected to the tumor homing moiety through a linker that releases the drug inside or in proximity of the tumor cell, and that represents a key component for the final therapeutic effect of the conjugate. Here, we show that the replacement of the Val-Ala-p-aminobenzyloxycarbamate linker with the Gly-Pro-Leu-Glyp-aminobenzyloxycarbamate (GPLG-PABC) sequence as enzymatically cleavable linker in the SMDC bearing the cyclo[DKP-isoDGR] aVß3 integrin ligand as tumor homing moiety and the monomethyl auristatin E (MMAE) as cytotoxic payload led to a 4-fold more potent anti-tumoral effect of the final conjugate on different cancer cell lines. In addition, the synthesized conjugate resulted to be significantly more potent than the free MMAE when tested following the "kiss-and-run" protocol, and the relative potency were clearly consistent with the expression of the aVß3 integrin receptor in the considered cancer cell lines. In vitro enzymatic cleavage tests showed that the GPLG-PABC linker is cleaved by lysosomal enzymes, and that the released drug is observable already after 15 min of incubation. Although additional data are needed to fully characterize the releasing capacity of GPLG-PABC linker, our findings are of therapeutic significance since we are introducing an alternative to other well-established enzymatically sensitive peptide sequences that might be used in the future for generating more efficient and less toxic drug delivery systems. [ABSTRACT FROM AUTHOR]

Prostate cancer is the second most common cancer among men. We designed and synthesized new ligands targeting prostate-specific membrane antigen and suitable for bimodal conjugates with diagnostic and therapeutic agents. In vitro studies of the affinity of the synthesized compounds to the protein target have been carried out. Based on these ligands, a series of bimodal conjugates with a combination of different mitosis inhibitors and antiandrogenic drugs were synthesized. The cytotoxicity of the compounds obtained in vitro was investigated on three different cell lines. The efficacy of the two obtained conjugates was evaluated in vivo in xenograft models of prostate cancer. These compounds have been shown to be highly effective in inhibiting the growth of PSMA-expressing tumors. [ABSTRACT FROM AUTHOR]

Objective: To review and compare the pharmacology, efficacy, and safety of the novel tissue factor antibody–drug conjugate, tisotumab vedotin Data sources: Literature search was performed through PubMed MEDLINE, Google Scholar, ClinicalTrials.gov, and the Food and Drug Administration. Data summary: Tisotumab vedotin, a novel tissue factor antibody–drug conjugate, was granted accelerated approval by the US FDA on 20 September 2021 for adult patients with recurrent or metastatic cervical cancer with disease progression on or after chemotherapy. Tisotumab vedotin demonstrated clinical efficacy in a number of solid tumors in innovaTV 201 and more specifically in cervical cancer in the pivotal phase 2 innovaTV 204. In the single-arm innovaTV 204 study, 101 patients with recurrent or metastatic cervical cancer received intravenous tisotumab vedotin at the recommended dose of 2 mg/kg every 3 weeks until disease progression or unacceptable toxicity. The independent review committee confirmed an objective response rate of 24% with 7% complete responses and 17% partial responses. Tisotumab vedotin is associated with several notable adverse events with data from innovaTV 204 including ocular toxicity, hemorrhage, and peripheral neuropathy. Ninety-two percent of patients experienced treatment-related adverse events with 28% experiencing an adverse event of grade 3 or higher. Conclusions: Metastatic cervical cancer has a high risk of relapse with few effective second-line therapeutic options. Current guidelines recommend single agent tisotumab vedotin as a possible option. Ongoing trials will further define its place in therapy. [ABSTRACT FROM AUTHOR]

Antibody-Drug Conjugates (ADCs) and Small Molecule-Drug Conjugates (SMDCs) represent successful examples of targeted drug-delivery technologies for overcoming unwanted side effects of conventional chemotherapy in cancer treatment. In both strategies, a cytotoxic payload is connected to the tumor homing moiety through a linker that releases the drug inside or in proximity of the tumor cell, and that represents a key component for the final therapeutic effect of the conjugate. Here, we show that the replacement of the Val-Ala-p-aminobenzyloxycarbamate linker with the Gly-Pro-Leu-Gly-p-aminobenzyloxycarbamate (GPLG-PABC) sequence as enzymatically cleavable linker in the SMDC bearing the cyclo[DKP-isoDGR] αVβ3 integrin ligand as tumor homing moiety and the monomethyl auristatin E (MMAE) as cytotoxic payload led to a 4-fold more potent anti-tumoral effect of the final conjugate on different cancer cell lines. In addition, the synthesized conjugate resulted to be significantly more potent than the free MMAE when tested following the “kiss-and-run” protocol, and the relative potency were clearly consistent with the expression of the αVβ3 integrin receptor in the considered cancer cell lines. In vitro enzymatic cleavage tests showed that the GPLG-PABC linker is cleaved by lysosomal enzymes, and that the released drug is observable already after 15 min of incubation. Although additional data are needed to fully characterize the releasing capacity of GPLG-PABC linker, our findings are of therapeutic significance since we are introducing an alternative to other well-established enzymatically sensitive peptide sequences that might be used in the future for generating more efficient and less toxic drug delivery systems.

A promising molecular target for aggressive cancers is the urokinase receptor (uPAR). A fully human, recombinant antibody that binds uPAR to form a stable complex that blocks uPA-uPAR interactions (2G10) and is internalized primarily through endocytosis showed efficacy in a mouse xenograft model of highly aggressive, triple negative breast cancer (TNBC). Antibody-drug conjugates (ADCs) of 2G10 were designed and produced bearing tubulin inhibitor payloads ligated through seven different linkers. Aldehyde tag technology was employed for linking, and either one or two tags were inserted into the antibody heavy chain, to produce site-specifically conjugated ADCs with drug-to-antibody ratios of either two or four. Both cleavable and non-cleavable linkers were combined with two different antimitotic toxins-MMAE (monomethylauristatin E) and maytansine. Nine different 2G10 ADCs were produced and tested for their ability to target uPAR in cell-based assays and a mouse model. The anti-uPAR ADC that resulted in tumor regression comprised an MMAE payload with a cathepsin B cleavable linker, 2G10-RED-244-MMAE. This work demonstrates in vitro activity of the 2G10-RED-244-MMAE in TNBC cell lines and validates uPAR as a therapeutic target for TNBC.

An improved series of ligands targeting prostatic specific membrane antigen has been reported. Varying compounds and their biological parameters were due to changes in the linker structure. Highly selective compounds with nanomolar IC50 values were obtained. As an example, a conjugate with Sulfo-Cy5 and MMAE was obtained and pre-studied. [ABSTRACT FROM AUTHOR]

Chemotherapy for hemodialysis (HD) patients is a challenging situation because HD patients are generally frail, and the pharmacokinetics and pharmacodynamics of most chemotherapeutics in HD patients are unknown. We report a classical Hodgkin lymphoma (cHL) patient successfully treated with 34 courses of brentuximab vedotin (BV) monotherapy, of which 30 courses were carried out during HD. Although grade 2 peripheral sensory neuropathy and one occasion of febrile neutropenia were observed, treatment was well-tolerated overall and effective. This is the first report of successful BV administration in a cHL patient on HD, and also the first to report efficacy and safety of extended courses of BV in an HD patient. Treatment options for cHL in the HD patient are limited, and extended courses of BV monotherapy may be an optimal treatment approach for some patients.

We designed and developed 9MW2821, an anti-Nectin-4 antibody–drug conjugate (ADC) with an enzymatically cleavable valine–citrulline linker and monomethyl auristatin E (MMAE) as the payload. Four bioanalytical assays for total antibodies, conjugated antibodies, conjugated payload, and free payload were then developed and validated for the comprehensive evaluation of the multiple drug forms of 9MW2821. Specific sandwich enzyme-linked immunosorbent assays were used to quantify total antibodies and conjugated antibody, showing good drug-to-antibody ratio (DAR) tolerance. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine free MMAE, and conjugated MMAE was quantified using a combination of ligand-binding assay (LBA) and LC-MS/MS. Based on these four assays, we studied the serum stability and monkey pharmacokinetic profiles of 9MW2821, and the in vivo DAR of 9MW2821 was calculated and dynamically monitored. In conclusion, we developed and validated series of bioanalytical assays to quantify multiple forms of 9MW2821, a new ADC, and used the assays to evaluate the serum stability and monkey pharmacokinetic characteristics. The results indicate good linker stability and suggest that the developed assays can be further used in clinical settings. • Transformation of ADC in vivo must be considered when developing bioanalysis assay. • Conjugated antibody with low-DAR can be captured using MMAE mAb with high affinity. • Conjugated MMAE is quantified using a combination of LBA and LC-MS/MS. • The DAR of 9MW2821 is dynamically monitored, indicating good linker stability. [ABSTRACT FROM AUTHOR]

A prodrug is bioreversible medication that is specifically converted to the active drugs by enzymes overexpressed in the tumor microenvironment, which can considerably reduce the chemotherapy-induced side effects. However, prodrug strategies usually have low antitumor efficacy compared to free drugs by delayed drug release. This is because they need time to be activated by enzymatic cleavage and they also cannot be fully recovered to the active drugs. Therefore, highly potent anticancer drug should be considered to expect a sufficient antitumor efficacy. Herein, we propose tumor-specific monomethyl auristatin E (MMAE) prodrug nanoparticles for safe and effective chemotherapy. The cathepsin B-specific cleavable FRRG peptide and MMAE are chemically conjugated via one-step simple synthetic chemistry. The resulting FRRG-MMAE molecules form stable nanoparticles without any additional carrier materials by hydrophobic interaction-derived aggregations. The FRRG-MMAE nanoparticles efficiently accumulate within the tumor tissues owing to the enhanced permeability and retention (EPR) effect and inhibit the tubulin polymerization by releasing free MMAE in the cathepsin B-overexpressed tumor cells. In contrast, FRRG-MMAE nanoparticles maintain a non-toxic inactive state in the normal tissues owing to innately low cathepsin B expression, thereby reducing MMAE-related severe toxicity. Collectively, this study provides a promising approach for safe and effective chemotherapy via MMAE-based prodrug nanoparticles, which may open new avenues for advanced drug design for translational nanomedicine. [ABSTRACT FROM AUTHOR]

Antibody-drug conjugates (ADCs) have been recognized as a promising class of cancer therapeutics. Tissue factor (TF), an initiator of the blood coagulation pathway, has been investigated regarding its relationship with cancer, and several preclinical and clinical studies have presented data on anti-TF ADCs, including tisotumab vedotin, which was approved in 2021. However, the feasibility of other payloads in the design of anti-TF ADCs is still unclear because no reports have compared payloads with different cytotoxic mechanisms. For ADCs targeting other antigens, such as Her2, optimizing the payload is also an important issue in order to improve in vivo efficacy. In this study, we prepared humanized anti-TF Ab (clone.1084) conjugated with monomethyl auristatin E (MMAE) or deruxtecan (DXd), and evaluated the efficacy in several cell line- and patient-derived xenograft models of pancreatic cancer. As a result, optimizing the drug / Ab ratio was necessary for each payload in order to prevent pharmacokinetic deterioration and maximize delivery efficiency. In addition, MMAE-conjugated anti-TF ADC showed higher antitumor effects in tumors with strong and homogeneous TF expression, while DXd-conjugated anti-TF ADC was more effective in tumors with weak and heterogeneous TF expression. Analysis of a pancreatic cancer tissue array showed weak and heterogeneous TF expression in most TF-positive specimens, indicating that the response rate to pancreatic cancer might be higher for DXd- than MMAE-conjugated anti-TF ADC. Nevertheless, our findings indicated that optimizing the ADC payloads individually in each patient could maximize the potential of ADC therapeutics., (© 2024 The Author(s). Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.)

Prostate cancer is the second most common cancer among men. We designed and synthesized new ligands targeting prostate-specific membrane antigen and suitable for bimodal conjugates with diagnostic and therapeutic agents. In vitro studies of the affinity of the synthesized compounds to the protein target have been carried out. Based on these ligands, a series of bimodal conjugates with a combination of different mitosis inhibitors and antiandrogenic drugs were synthesized. The cytotoxicity of the compounds obtained in vitro was investigated on three different cell lines. The efficacy of the two obtained conjugates was evaluated in vivo in xenograft models of prostate cancer. These compounds have been shown to be highly effective in inhibiting the growth of PSMA-expressing tumors.

Antibody-drug conjugates (ADCs) are commonly heterogeneous and require extensive assessment of exposure-efficacy and exposure-safety relationships in preclinical and clinical studies. In this study, we report the generation of a monoclonal antibody against monomethyl auristatin E (MMAE) and the development, validation, and application of sensitive and high-throughput enzyme-linked immunosorbent assays (ELISA) to measure the concentrations of MMAE-conjugated ADCs and total antibodies (tAb, antibodies in ADC plus unconjugated antibodies) in cynomolgus monkey sera. These assays were successfully applied to in vitro plasma stability and pharmacokinetic (PK) studies of SMADC001, an MMAE-conjugated ADC against trophoblast cell surface antigen 2 (TROP-2). The plasma stability of SMADC001 was better than that of similar ADCs coupled with PEG4-Val-Cit, Lys (m-dPEG24)-Cit, and Val-Cit linkers. The developed ELISA methods for the calibration standards of ADC and tAb revealed a correlation between serum concentrations and the OD 450 values, with R 2 at 1.000, and the dynamic range was 0.3–35.0 ng/mL and 0.2–22.0 ng/mL, respectively; the intra- and inter-assay accuracy bias% ranged from −12.2% to −5.2%, precision ranged from −12.4% to −1.4%, and the relative standard deviation (RSD) was less than 6.6% and 8.7%, respectively. The total error was less than 20.4%. The development and validation steps of these two assays met the acceptance criteria for all addressed validation parameters, which suggested that these can be applied to quantify MMAE-conjugated ADCs, as well as in PK studies. Furthermore, these assays can be easily adopted for development of other similar immunoassays. [Display omitted] • A specific monoclonal antibody against MMAE was generated via hybridoma technology. • ELISA was used to quantify MMAE-ADCs with a calibration range of 0.5–35 ng/mL. • ELISA was used to quantify total antibodies with a calibration range of 0.6–22 ng/mL. • Pharmacokinetic profiles of SMADC001 in cynomolgus monkeys were investigated. [ABSTRACT FROM AUTHOR]

Purpose: Antibody-drug conjugates (ADCs) have emerged as a potent cancer therapeutic option in recent years. DP303c is a HER2-targeting ADC with a cleavable linker-MMAE payload. The current study aimed to evaluate the therapeutic potentials of DP303c in vitro as well as in vivo. Materials and Methods: Size exclusion chromatography (SEC), reverse-phase high-performance liquid chromatography (RP-HPLC), and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to analyze the physicochemical characterization of DP303c. An enzyme-linked immunosorbent assay (ELISA), a cell-based assay, and bio-layer interferometry (BLI) were used to evaluate DP303c's affinity with HER2 and Fc receptors. A confocal laser scanning microscopy was used to observe the internalization of DP303c. Antibody-dependent cell-mediated cytotoxicity (ADCC) and cytotoxicity assays were used to investigate the activity of DP303c in vitro. The antitumor activity of DP303c was assessed in vivo in the HER2-positive cell-derived xenograft model. Results: DP303c was a site-specific anti-HER2 antibody-drug conjugate with a monomethyl auristatin E (MMAE) with an average drug-to-antibody ratio (DAR) of 2.0. DP303c showed a high affinity with HER2 and could be effectively internalized. In vitro and in vivo, DP303c showed stronger antitumor activity as compared to trastuzumab-DM1 (T-DM1) in a series of HER2-positive cancer cells and cell-derived xenograft (CDX) models, especially in the lower HER2-expressing cells. DP303c also exhibited high serum stability and a good PK profile. Conclusion: DP303c was a steady and homogenous DAR 2 ADC that was predicted to deliver MMAE inhibitor to tumor cells. DP303c demonstrated remarkable anticancer efficacy against T-DM1 in xenograft models. DP303c was a strong candidate for the treatment of patients with HER2-positive cancer. [ABSTRACT FROM AUTHOR]

Chemotherapy for hemodialysis (HD) patients is a challenging situation because HD patients are generally frail, and the pharmacokinetics and pharmacodynamics of most chemotherapeutics in HD patients are unknown. We report a classical Hodgkin lymphoma (cHL) patient successfully treated with 34 courses of brentuximab vedotin (BV) monotherapy, of which 30 courses were carried out during HD. Although grade 2 peripheral sensory neuropathy and one occasion of febrile neutropenia were observed, treatment was well-tolerated overall and effective. This is the first report of successful BV administration in a cHL patient on HD, and also the first to report efficacy and safety of extended courses of BV in an HD patient. Treatment options for cHL in the HD patient are limited, and extended courses of BV monotherapy may be an optimal treatment approach for some patients. [ABSTRACT FROM AUTHOR]

A prodrug is bioreversible medication that is specifically converted to the active drugs by enzymes overexpressed in the tumor microenvironment, which can considerably reduce the chemotherapy-induced side effects. However, prodrug strategies usually have low antitumor efficacy compared to free drugs by delayed drug release. This is because they need time to be activated by enzymatic cleavage and they also cannot be fully recovered to the active drugs. Therefore, highly potent anticancer drug should be considered to expect a sufficient antitumor efficacy. Herein, we propose tumor-specific monomethyl auristatin E (MMAE) prodrug nanoparticles for safe and effective chemotherapy. The cathepsin B-specific cleavable FRRG peptide and MMAE are chemically conjugated via one-step simple synthetic chemistry. The resulting FRRG-MMAE molecules form stable nanoparticles without any additional carrier materials by hydrophobic interaction-derived aggregations. The FRRG-MMAE nanoparticles efficiently accumulate within the tumor tissues owing to the enhanced permeability and retention (EPR) effect and inhibit the tubulin polymerization by releasing free MMAE in the cathepsin B-overexpressed tumor cells. In contrast, FRRG-MMAE nanoparticles maintain a non-toxic inactive state in the normal tissues owing to innately low cathepsin B expression, thereby reducing MMAE-related severe toxicity. Collectively, this study provides a promising approach for safe and effective chemotherapy via MMAE-based prodrug nanoparticles, which may open new avenues for advanced drug design for translational nanomedicine.

• Humanized anti-glypican-1 antibody was conjugated with monomethyl auristatin E. • Elevated glypican-1 expression was shown in glioblastoma by immunohistochemistry. • GPC1-ADC bound to GPC1 was efficiently internalized in glioblastoma cell lines. • An orthotopic xenograft was established by intracranial implantation of KS-1-Luc. • Intravenous administration of GPC1-ADC showed potent intracranial activity. Glioblastoma is the deadliest form of brain tumor. The presence of the blood–brain barrier (BBB) significantly hinders chemotherapy, necessitating the development of innovative treatment options for this tumor. This report presents the in vitro and in vivo efficacy of an antibody–drug conjugate (ADC) that targets glypican-1 (GPC1) in glioblastoma. The GPC1-ADC was created by conjugating a humanized anti-GPC1 antibody (clone T2) with monomethyl auristatin E (MMAE) via maleimidocaproyl-valine-citrulline-p-aminobenzyloxycarbonyl linkers. Immunohistochemical staining analysis of a glioblastoma tissue microarray revealed that GPC1 expression was elevated in more than half of the cases. GPC1-ADC, when bound to GPC1, was efficiently and rapidly internalized in glioblastoma cell lines. It inhibited the growth of GPC1-positive glioma cell lines by inducing cell cycle arrest in the G2/M phase and triggering apoptosis in vitro. We established a heterotopic xenograft model by subcutaneously implanting KALS-1 and administered GPC1-ADC intravenously. GPC1-ADC significantly inhibited tumor growth and increased the number of mitotic cells. We also established an orthotopic xenograft model by intracranially implanting luciferase-transfected KS-1-Luc#19. After injecting Evans blue and resecting brain tissues, dye leakage was observed in the implantation area, confirming BBB disruption. We administered GPC1-ADC intravenously and measured the luciferase activity using an in vivo imaging system. GPC1-ADC significantly inhibited tumor growth and extended survival. In conclusion, GPC1-ADC demonstrated potent intracranial activity against GPC1-positive glioblastoma in an orthotopic xenograft model. These results indicate that GPC1-ADC could represent a groundbreaking new therapy for treating glioblastoma beyond the BBB. [ABSTRACT FROM AUTHOR]

[Display omitted] The favorable benefit–risk profile of polatuzumab vedotin, as demonstrated in a pivotal Phase Ib/II randomized study (GO29365; NCT02257567), coupled with the need for effective therapies in relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL), prompted the need to accelerate polatuzumab vedotin development. An integrated, fit-for-purpose clinical pharmacology package was designed to support regulatory approval. To address key clinical pharmacology questions without dedicated clinical pharmacology studies, we leveraged non-clinical and clinical data for polatuzumab vedotin, published clinical data for brentuximab vedotin, a similar antibody–drug conjugate, and physiologically based pharmacokinetic and population pharmacokinetic modeling approaches. We review strategies and model-informed outcomes that contributed to regulatory approval of polatuzumab vedotin plus bendamustine and rituximab in R/R DLBCL. These strategies made polatuzumab vedotin available to patients earlier than previously possible; depending on the strength of available data and the regulatory/competitive environment, they may also prove useful in accelerating the development of other agents. [ABSTRACT FROM AUTHOR]

To harness the intrinsic transport properties of albumin yet improve the therapeutic index of current in situ albumin-binding prodrugs, we developed albumin-drug conjugates with a controlled loading that achieved better antitumor efficacy. Here, model drug monomethyl auristatin E (MMAE) was conjugated ex vivo to Cys34 of albumin via a cathepsin B-sensitive dipeptide linker to ensure that all drug would be bound specifically to albumin. The resulting albumin-drug conjugate with a drug to albumin ratio (DAR) of 1 (ALDC1) retained the native secondary structure of albumin compared to conjugate with a higher DAR of 3 (ALDC3). ALDC1 exhibited improved drug release and cytotoxicity compared to ALDC3 in vitro. Slower plasma clearance and increased drug exposure over time of ALDC1 were observed compared to ALDC3 and MMAE prodrug. In single dose studies with MIA PaCa2 xenografts, cohorts treated with ALDC1 had the highest amount of MMAE drug in tumor tissues compared to other treatment arms. After multiple dosing, ALDC1 significantly delayed the tumor growth compared to control treatment arms MMAE, MMAE-linker conjugate and ALDC3. When dosed with the maximum tolerated dose of ALDC1, there was complete eradication of 83.33% of the tumors in the treatment group. Ex vivo conjugated ALDC1 also significantly inhibited tumor growth in an immunocompetent syngeneic mouse model that better recapitulates the phenotype and clinical features of human pancreatic cancers. In summary, site-specific loading of drug to albumin at 1:1 ratio allowed the conjugate to better maintain the native structure of albumin and its intrinsic properties. By conjugating the drug to albumin prior to administration minimized premature cleavage and instability of the drug in plasma and enabled higher drug accumulation in tumors compared to in situ albumin-binding prodrugs. This strategy to control drug loading ex vivo ensures complete drug binding to the albumin carrier and achieves excellent antitumor efficacy, and it has the potential to greatly improve the outcomes of anticancer therapy. Unlabelled Image • Albumin-drug conjugates with site-specific conjugation at Cys34 ex vivo enhanced drug delivery and antitumor efficacy. • Controlled loading of drugs minimized the change in albumin structure and is crucial to higher drug accumulation in tumors. • Ex vivo conjugation reduced premature release of the active drug compared to in situ albumin binding prodrug. • Ex vivo conjugation improved tumor regression in different models of pancreatic cancer compared to in situ binding prodrugs. [ABSTRACT FROM AUTHOR]

This study investigated the safety and tolerability of lifastuzumab vedotin (DNIB0600A) (LIFA), an antibody-drug conjugate, in patients with recurrent platinum-sensitive ovarian cancer (PSOC). In this open-label, multicenter phase 1b study, LIFA was administered intravenously once every 3 weeks (Q3W) with starting dose 1.2 mg/kg in a 3 + 3 dose-escalation scheme. All patients received carboplatin at dose AUC 6 mg/mL·min (AUC6) Q3W for up to 6 cycles. Dose expansion cohorts were enrolled ± bevacizumab 15 mg/kg Q3W. Patients received LIFA at 1.2, 1.8, and 2.4 mg (n = 4, 5, and 20, respectively) with carboplatin. The maximum tolerated dose was not reached. The recommended phase 2 dose (RP2D) was LIFA 2.4 mg/kg + carboplatin AUC6 (cycles 1–6), with or without bevacizumab 15 mg/kg. Twelve patients received RP2D with bevacizumab. All patients experienced ≥1 adverse event (AE). The most common treatment-related AEs were neutropenia, peripheral neuropathy, thrombocytopenia, nausea, fatigue, anemia, diarrhea, vomiting, hypomagnesaemia, aspartate aminotransferase increased, alanine aminotransferase increased, and alopecia. Thirty-four (83%) patients experienced grade ≥ 3 AEs, the most frequent of which were neutropenia and thrombocytopenia. Nine (22%) patients experienced serious AEs. Pulmonary toxicities (34%), considered a potential risk of LIFA, included one patient who discontinued study treatment due to grade 2 pneumonitis. The median duration of progression-free survival was 10.71 months (95% CI: 8.54, 13.86) with confirmed complete/partial responses in 24 (59%) patients. Pharmacokinetics of mono-therapy LIFA was similar in combination therapy. LIFA in combination with carboplatin ± bevacizumab demonstrated acceptable safety and encouraging activity in PSOC patients. • Lifastuzumab vedotin DNIB0600A (LIFA) is an anti-NaPi2b antibody conjugated to a potent anti-mitotic agent (MMAE). • This phase Ib study investigated LIFA in patients with recurrent platinum-sensitive ovarian cancer. • LIFA in combination with carboplatin has an acceptable safety profile when administered by IV infusion Q3W. • Overall confirmed objective responses were observed in 59% and CA-125 responses in 81% of evaluable patients. • Response rate and duration of response are important factors for evaluation of antibody-drug conjugates in ovarian cancers. [ABSTRACT FROM AUTHOR]

Background: Monomethyl auristatin E (MMAE) is a synthetic analog of dolastatin 10, a compound originally isolated from the marine mollusk. MMAE, as a highly potent microtubule inhibitor, exerts its potent cytotoxic effect by inhibiting microtubule assembly, tubulin-dependent GTP hydrolysis and microtubes polymerization. This molecule, by itself, lacks the tumor specificity required to elicit therapeutic benefit. Nevertheless, the extremely cytotoxic potential of MMAE could be harnessed in the form of MMAE-antibody conjugates. The aim of the present study was to evaluate the cytotoxic activity of MMAE against breast (SKBR3) and kidney (HEK293) cancer cell lines in an in vitro cell-based assay.Materials and Methods: SKBR3 and HEK293 cells were treated with different concentrations ranging from 0.002048, 0.01024, 0.0512, 0.256, 1.28, 6.4, 32, 160, 800 and 4000 nM of MMAE, and cell viability was determined after 72 hours using an MTT colorimetric assay. The effect of MMAE was regularly monitored by direct observation using an invert microscope.Results: Microscopic observation showed that there was a concentration-dependent increase in cell death. Results from the MTT assay revealed a statistically significant loss of viability (PConclusion: MMAE was able to significantly inhibit cell growth at nanomolar concentrations, emphasizing its great potential for the development of antibody-drug conjugates.

Antibody-drug conjugates (ADCs) are composed of an antibody linked to cytotoxic anticancer payloads. ADCs recognize tumor-specific cell surface antigens and are internalized into lysosomes where proteolytic enzymes release the cytotoxic payloads. Efflux transporters on plasma membrane that play a significant role on multi-drug resistance in chemotherapy can be internalized on lysosomal membrane and sequester the cytotoxic payloads. In the present study, ATP binding cassette (ABC) efflux transporters including breast cancer resistance protein (BCRP), P-glycoprotein (P-gp-MDR1), multidrug resistance protein (MRP) 2, MRP3 and MRP4 in lysosomal, and plasma membrane of tumor cells were quantified by targeted quantitative proteomics. The cytotoxicity of brentuximab vedotin and its cytotoxic payload monomethyl auristatin E (MMAE) to the tumor cell lines in the presence and absence of elacridar (P-gp-MDR1 inhibitor) or chloroquine (lysosomotropic agent) were evaluated. MMAE is a substrate for P-gp-MDR1, as the apparent efflux ratio in MDR1 transfected MDCK cell monolayers was 44.5, and elacridar abolished the MMAE efflux. Cell lines that highly express P-gp-MDR1 show higher EC50s toward the cell killing effects of MMAE. Co-incubation with chloroquine or elacridar resulted in left shift of MMAE EC50 by 2.9–16-fold and 4.2–22-fold, respectively. Similarly co-incubation with chloroquine or elacridar or in combination of chloroquine and elacridar increased cytotoxic effects of brentuximab vedotin by 2.8- to 21.4-fold on KM-H2 cells that express a specific tumor antigen CD30 and P-gp-MDR1. These findings demonstrate important roles of P-gp-MDR1 on cytotoxic effects of brentuximab vedotin and its payload MMAE. Collectively, ABC transporter-mediated drug extrusion and/or sequestration needs to be early assessed for selection of optimal payloads and linkers when developing ADCs.

Background: The Bicycle ® toxin conjugate BT5528 is a novel peptide therapeutic conjugated to the cytotoxic agent monomethyl auristatin E (MMAE). A bioanalytical assay was developed to quantify BT5528 and unconjugated MMAE in human plasma. Methodology: BT5528 quantitation used a protein precipitation procedure followed by LC-MS/MS detection. Quantitation of MMAE required a selective offline and online solid-phase extraction with detection via LC-MS/MS. Results: BT5528 was quantified over the assay range of 5-2500 ng/ml and free MMAE was quantified over the assay range of 0.05-50 ng/ml. Conclusion: Bioanalytical methods were used in the bioanalysis of intact BT5528 and released MMAE, in a phase I/IIa clinical trial; to date, over 2000 human patient samples have been analyzed.

Prostate stem cell antigen (PSCA) is expressed in all stages of prostate cancer, including in advanced androgen-independent tumors and bone metastasis. PSCA may associate with prostate carcinogenesis and lineage plasticity in prostate cancer. PSCA is also a promising theranostic marker for a variety of other solid tumors, including pancreatic adenocarcinoma and renal cell carcinoma. Here, we identified a novel fully human PSCA antibody using phage display methodology. The structure-based affinity maturation yielded a high-affinity binder, F12, which is highly specific and does not bind to 6,000 human membrane proteins based on a membrane proteome array assay. F12 targets PSCA amino acids 63-69 as tested by the peptide scanning microarray, and it cross-reacts with the murine PSCA. IgG1 F12 efficiently internalizes into PSCA-expressing tumor cells. The antimitotic reagent monomethyl auristatin E (MMAE)-conjugated IgG1 F12 (ADC, F12-MMAE) exhibits dose-dependent efficacy and specificity in a human prostate cancer PC-3-PSCA xenograft NSG mouse model. This is a first reported ADC based on a fully human PSCA antibody and MMAE that is characterized in a xenograft murine model, which warrants further optimizations and investigations in additional preclinical tumor models, including prostate and other solid tumors.

Novel nanomedicines have been engineered to deliver molecules with therapeutic potentials, overcoming drawbacks such as poor solubility, toxicity or short half-life. Lipid-based carriers such as liposomes represent one of the most advanced classes of drug delivery systems. A Monomethyl Auristatin E (MMAE) warhead was grafted on a lipid derivative and integrated in fusogenic liposomes, following the model of antibody drug conjugates. By modulating the liposome composition, we designed a set of particles characterized by different membrane fluidities as a key parameter to obtain selective uptake from fibroblast or prostate tumor cells. Only the fluid liposomes made of palmitoyl-oleoyl-phosphatidylcholine and dioleoyl-phosphatidylethanolamine, integrating the MMAE-lipid derivative, showed an effect on prostate tumor PC-3 and LNCaP cell viability. On the other hand, they exhibited negligible effects on the fibroblast NIH-3T3 cells, which only interacted with rigid liposomes. Therefore, fluid liposomes grafted with MMAE represent an interesting example of drug carriers, as they can be easily engineered to promote liposome fusion with the target membrane and ensure drug selectivity.

Antibody-drug conjugates (ADCs) are composed of an antibody linked to cytotoxic anticancer payloads. ADCs recognize tumor-specific cell surface antigens and are internalized into lysosomes where proteolytic enzymes release the cytotoxic payloads. Efflux transporters on plasma membrane that play a significant role on multi-drug resistance in chemotherapy can be internalized on lysosomal membrane and sequester the cytotoxic payloads. In the present study, ATP binding cassette (ABC) efflux transporters including breast cancer resistance protein (BCRP), P-glycoprotein (P-gp-MDR1), multidrug resistance protein (MRP) 2, MRP3 and MRP4 in lysosomal, and plasma membrane of tumor cells were quantified by targeted quantitative proteomics. The cytotoxicity of brentuximab vedotin and its cytotoxic payload monomethyl auristatin E (MMAE) to the tumor cell lines in the presence and absence of elacridar (P-gp-MDR1 inhibitor) or chloroquine (lysosomotropic agent) were evaluated. MMAE is a substrate for P-gp-MDR1, as the apparent efflux ratio in MDR1 transfected MDCK cell monolayers was 44.5, and elacridar abolished the MMAE efflux. Cell lines that highly express P-gp-MDR1 show higher EC50s toward the cell killing effects of MMAE. Co-incubation with chloroquine or elacridar resulted in left shift of MMAE EC50 by 2.9–16-fold and 4.2–22-fold, respectively. Similarly co-incubation with chloroquine or elacridar or in combination of chloroquine and elacridar increased cytotoxic effects of brentuximab vedotin by 2.8- to 21.4-fold on KM-H2 cells that express a specific tumor antigen CD30 and P-gp-MDR1. These findings demonstrate important roles of P-gp-MDR1 on cytotoxic effects of brentuximab vedotin and its payload MMAE. Collectively, ABC transporter-mediated drug extrusion and/or sequestration needs to be early assessed for selection of optimal payloads and linkers when developing ADCs. [ABSTRACT FROM AUTHOR]

Stimuli-responsive polymer-drug conjugates (PDCs) provide promising approaches in anticancer treatment. Here, we report the synthesis and biological evaluation of PDCs made of the highly potent antimitotic agent monomethyl auristatin E conjugated to dendritic polyglycerol and dendritic polyglycerol sulfate via a reductively cleavable, self-immolative disulfide linker. Cell viability assays with the human cancer cell lines A549 (lung carcinoma) and HeLa (cervix carcinoma) revealed that the drug's cytotoxicity was reduced by conjugation to the polymers, with the sulfated conjugates being more effective than the non-sulfated ones. Kinetic studies using real-time cell analysis indicated a retarded drug release from the polymers, with a much later cytotoxic response after treatment with the non-sulfated conjugates due to less cellular uptake, as confirmed by flow cytometry and confocal laser scanning microscopy. In contrast, the non-cleavable dPGS-MMAE conjugate that was synthesized for comparison was not cytotoxic under the same conditions. Overall, reductively cleavable dPGS-SS-MMAE conjugates showed promising results in vitro and good tolerability in vivo. Further in vivo studies are planned. Polymer targeting by sulfate groups enables drug delivery in tumor cells. Unlabelled Image [ABSTRACT FROM AUTHOR]

Targeted therapy using specific monoclonal antibodies (mAbs) conjugated to chemotherapeutic agents or toxins has become one of the top priorities in cancer therapy. Antibody–drug conjugates (ADCs) are emerging as a promising strategy for cancer‐targeted therapy. In this study, trastuzumab, a humanized monoclonal anti‐HER2 antibody, was reduced by dithiothreitol and conjugated to the microtubule‐disrupting agent monomethyl auristatin E (MMAE) through a valine‐citrulline peptide linker (trastuzumab‐MC‐Val‐Cit‐PABC‐MMAE [trastuzumab‐vcMMAE]). After conjugation, ADCs were characterized by using UV–vis, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE), and flow cytometry. The antitumor activity of the ADC was evaluated in breast cancer cells in vitro. In addition, ADCs were further characterized using purification by the protein A chromatography, followed by assessment using apoptosis and MTT (3‐(4,5‐dimethylthiazol‐2‐yl)‐2, 5‐diphenyltetrazolium bromide) assays. Hydrophobic interaction chromatography was used to determine drug‐to‐antibody ratio species of ADCs produced. Our finding showed that approximately 5.12 drug molecules were conjugated to each mAb. H2L2, H2L, HL, H2, H, and L forms of ADCs were detected in nonreducing SDS‐PAGE. The binding of trastuzumab‐vcMMAE to HER2‐positive cells was comparable with that of the parental mAb. The MTT assay showed that our ADCs induced significant cell death in HER2‐positive cells, but not in HER2‐negative cells. The ADCs produced was a mixture of species, unconjugated trastuzumab (14.147%), as well as trastuzumab conjugated with two (44.868%), four (16.886%), six (13.238%), and eight (10.861%) molecules of MMAE. These results indicated that MMAE‐conjugated trastuzumab significantly increases the cytotoxic activity of trastuzumab, demonstrating high affinity, specificity, and antitumor activity in vitro. Trastuzumab‐vcMMAE is an effective and selective agent for the treatment of HER2‐positive breast tumors. We constructed monomethyl auristatin E conjugated trastuzumab that leads to improved cytotoxic activity of trastuzumab. [ABSTRACT FROM AUTHOR]

Abstract Despite the emergence of advanced therapeutics such as targeted therapy and immunotherapy in the modern oncology, cytotoxic chemotherapy still remains as the first-line treatment option in a wide range of cancers attributing to its potency. Many endeavors have been made to overcome the toxicity issues of cytotoxic chemotherapy by improving the specific delivery to the tumor, with active tumor targeting being one of the most popular approaches. However, such an approach has been challenged by the intratumor heterogeneity and the lack of valid molecular target in many types of cancer. Here, we introduce a novel albumin-binding prodrug MPD02 that could specifically deliver highly potent cytotoxin monomethyl auristatin E (MMAE) to the tumor as an important component of chemoradiotherapy for the treatment of triple-negative breast cancer (TNBC). MPD02 was synthesized by conjugating MMAE to the C-terminus of the KGDEVD peptide via self-eliminating linker and introducing a maleimide group to the Lys side chain of the peptide. MPD02 was able to bind albumin after administration via maleimide group for an extended circulation time and metabolized into MMAE in tumor-specific manner by reacting with the caspase-3 upregulated in tumor by radiotherapy, exerting a highly potent anticancer effect with good safety profile in two different TNBC xenograft models. [ABSTRACT FROM AUTHOR]

Antibody-drug conjugates (ADCs) are anticancer drugs consisting of a monoclonal antibody, targeting selective tumor antigens, to which has been frequently associated a highly potent cytotoxic agent, the monomethyl auristatin E (MMAE) using a chemical linker. MMAE is a tubulin polymerization inhibitor derived from dolastin-10. These MMAE-ADCs are responsible for peripheral nerve toxicities. Our objective was to develop and characterize a mouse model of MMAE-induced peripheral neuropathy induced by free MMAE injections. MMAE was injected in Swiss mice at 50 μg/kg i.p. every other day for 7 weeks. Assessments of motor and sensory nerve functions were performed once a week on MMAE and Vehicle-treated mice. Sciatic nerve and paw skin were removed at the end of experiment for subsequent immunofluorescence and morphological analysis. MMAE did not affect motor coordination, muscular strength and heat nociception, but significantly induced tactile allodynia in MMAE-treated mice compared with Vehicle-treated mice from day 35 to day 49. MMAE significantly reduced myelinated and unmyelinated axon densities in sciatic nerves and led to a loss of intraepidermal nerve fiber in paw skin. In summary, long course of low dose of MMAE induced a peripheral sensory neuropathy associated with nerve degeneration, without general state alteration. This model may represent a ready accessible tool to screen neuroprotective strategies in the context of peripheral neuropathies induced by MMAE-ADCs. • Monomethyl auristatin E (MMAE) antibody-drug-conjugates (ADCs) induce neuropathies. • Long course of low dose unconjugated MMAE induces tactile allodynia in Swiss mice. • Pain induced by MMAE treatment is associated with sensory nerve degeneration. • This model is a tool for the management of neuropathies induced by the MMAE payload. [ABSTRACT FROM AUTHOR]

Rituximab is a chimeric monoclonal antibody directed against B-lymphocyte specific antigen CD20, which is used for the treatment of B-cell malignancies. However, the effectiveness of rituximab is limited partly due to treatment resistance. The aim of this study was to develop rituximab-based antibody drug conjugate (ADC) to enhance rituximab activity. In this study, monomethyl auristatin E (MMAE) was covalently conjugated to dithiothreitol -reduced rituximab via a valine-citrulline peptide linker (rituximab-vcMMAE). The conjugates were then characterized by using nonreducing sodium dodecyl sulfate-polyacrylamide electrophoresis (SDS-PAGE) and cell-based enzyme-linked immunosorbent assay (ELISA). The cytotoxic activity of the ADC was evaluated against Raji (human B-cell lymphoma; CD20-positive) and MOLT-4 (T lymphoblast; acute lymphoblastic leukemia; CD20-negative) cell lines. In addition, the colony formation assay was used to identify the propagation ability of ADC-treated cells in vitro. Results from nonreducing SDS-PAGE revealed various species of rituximab-MC-Val-Cit-PABC-MMAE (rituximab-vcMMAE), as compared with unconjugated rituximab. The binding capacity of rituximab-vcMMAE to the CD20-positive cell was similar to that of the parental rituximab. Most importantly, our results revealed that rituximab-vcMMAE was highly potent against the CD20-positive cell line, but not against the CD20-negative cell. At the same time, rituximab-vcMMAE was able to inhibit colony formation in CD20-positive cells. These data indicate that rituximab-vcMMAE may be a highly effective and selective therapy for the treatment of B-cell lymphoma. [ABSTRACT FROM AUTHOR]

Several folate-drug conjugates are currently undergoing clinical trials for application in oncology. However, the efficacy of folate-targeted therapy strongly depends on the folate receptor (FR) abundance at the surface of cancer cells. Recently, it has been postulated that up-regulation of FRα by means of chemo-sensitizing agents could enhance the anticancer activity of FR-drug conjugates. In this study, we demonstrate in vitro that a combination of dexamethasone (Dexa) and valproic acid (VPA) increases FRα expression selectively at the surface of FR-overexpressing cancer cells. The same stimulation was observed in vivo in KB-tumor xenografts when mice are treated with this combined treatment. This effect is reversible since treatment interruption induces the return of FR expression at basal level. When incubated with Dexa and VPA, the β-galactosidase-responsive folate-monomethyl auristatin E (MMAE) conjugate, called MGAF, exhibits higher cytotoxic activity on several FR-positive human cancer cell lines, compared to its administration as a single agent. This improved toxicity results from the enhanced concentration of MMAE released within cancer cells after internalization and subsequent enzymatic activation of MGAF. Higher deposition of MMAE is also observed in vivo after up-regulation of FR expression level in tumor xenografts, induced by the prior administration of the Dexa/VPA combination. In this model, MGAF/Dexa/VPA combined therapy results in an 81% inhibition of tumor growth compared to the control group, while MGAF used in monotherapy is inefficient. Since Dexa and VPA are currently used in humans, this finding could be of great interest for further development of folate-drug conjugates, in particular for those that are presently under clinical investigation. [ABSTRACT FROM AUTHOR]

Prognosis in patients suffering from high-risk, refractory and relapsed germ cell tumours ( GCT) often comprising of CD30-positive embryonal carcinoma ( EC) components remains poor. Thus, novel treatment strategies are warranted. The antibody-drug conjugate ( ADC) brentuximab vedotin delivers the potent antimitotic drug monomethyl auristatin E ( MMAE) to CD30-expressing tumour cells. After CD30 binding, internalization and intracellular linker cleavage cytotoxic MMAE can efflux and eradicate neighbouring CD30-negative cells. To analyse cytotoxicity and a potential bystander effect of brentuximab vedotin in GCT, we established an in vitro coculture model mimicking GCT of heterogeneous CD30 positivity and measured cell viability, proliferation and apoptosis after exposure to brentuximab vedotin and unbound MMAE by MTS- and flow cytometry-based CFSE/Hoechst assay. CD30 expression being assessed by quantitative RT- PCR and immunohistochemistry was apparent in all EC cell lines with different intensity. Brentuximab vedotin abrogates cell viability of CD30-positive GCT27 EC line exerting marked time-dependent antiproliferative and pro-apoptotic activity. CD30-negative JAR cultured alone barely responds to brentuximab vedotin, while in coculture with GCT27 brentuximab vedotin induces clear dose-dependent cytotoxicity. Cellular proliferation and cell death are significantly enhanced in CD30-negative JAR cocultured with CD30-positive GCT27 compared to JAR cultured alone in proof of substantial bystander activity of brentuximab vedotin in CD30-negative GCT. We present first evidence that in an in vitro model mimicking GCT of heterogeneous histology, brentuximab vedotin exerts potent antiproliferative and pro-apoptotic activity against both CD30-positive as well as CD30-negative GCT subsets. Our results strongly support translational efforts to evaluate clinical efficacy of brentuximab vedotin in high-risk GCT of heterogeneous CD30 positivity. [ABSTRACT FROM AUTHOR]

Background: Monomethyl auristatin E (MMAE) is a synthetic analog of dolastatin 10, a compound originally isolated from the marine mollusk. MMAE, as a highly potent microtubule inhibitor, exerts its potent cytotoxic effect by inhibiting microtubule assembly, tubulin-dependent GTP hydrolysis and microtubes polymerization. This molecule, by itself, lacks the tumor specificity required to elicit therapeutic benefit. Nevertheless, the extremely cytotoxic potential of MMAE could be harnessed in the form of MMAE-antibody conjugates. The aim of the present study was to evaluate the cytotoxic activity of MMAE against breast (SKBR3) and kidney (HEK293) cancer cell lines in an in vitro cell-based assay. Materials and Methods: SKBR3 and HEK293 cells were treated with different concentrations ranging from 0.002048, 0.01024, 0.0512, 0.256, 1.28, 6.4, 32, 160, 800 and 4000 nM of MMAE, and cell viability was determined after 72 hours using an MTT colorimetric assay. The effect of MMAE was regularly monitored by direct observation using an invert microscope. Results: Microscopic observation showed that there was a concentration-dependent increase in cell death. Results from the MTT assay revealed a statistically significant loss of viability (P<0.0001) at concentrations ranging from 0.01024 to 4000 nM in SKBR3 cells, and 0.0512 to 4000 nM in HEK293 cells. Our findings showed that MMAE inhibited the growth of SKBR3 and HEK293 cells in a concentration-dependent manner, with IC50 values of 3.27 ± 0.42 and 4.24 ± 0.37 nM, respectively. Conclusion: MMAE was able to significantly inhibit cell growth at nanomolar concentrations, emphasizing its great potential for the development of antibody-drug conjugates. [ABSTRACT FROM AUTHOR]

Antibody-drug conjugates (ADCs), designed to selectively deliver cytotoxic agents to antigen-bearing cells, are poised to become an important class of cancer therapeutics. Human epithelial growth factor receptor (HER2) is considered an effective target for cancer treatment, and a HER2-targeting ADC has shown promising results. Most ADCs undergoing clinical evaluation contain linkers that have a lysosomal protease-cleavable dipeptide, of which the most common is valine-citrulline (VC). However, valine-alanine (VA), another dipeptide comprising two human essential amino acids, has been used in next generation ADCs loading new toxins, but the druggable properties of ADCs loaded the most popular monomethyl auristatin E (MMAE) remain to be further explored. In this study, we generated VA-based ADCs that connected MMAE to an anti-HER2 antibody. We studied the differences in the preparation process, in vitro stability, cathepsin B activity and in vitro cytotoxicity of VA-based ADC compared to the ADC of VC. VA had comparable performance to VC, which preliminarily displays its practicability. Additional efficacy and safety studies in a xenograft model indicate this novel ADC exerted potent anti-tumor activity and negligible toxicity. The results of this study show the application potential of VA-based ADC with MMAE as the payload. [ABSTRACT FROM AUTHOR]

Background: Breast cancer is a heterogeneous disease characterized by differential responses to targeted and chemotherapeutic agents. Antibody-drug conjugates are one of the promising strategies for the treatment of breast cancer. Monomethyl auristatin E (MMAE) is a highly potent microtubule inhibitor and a common payload used for development of antibody-drug conjugates. The purpose of this study was to investigate the cytotoxic effects of MMAE on breast cancer cell lines. Materials and Methods: MDA-MB-468 and MDA-MB-453 cells were treated with MMAE at various concentrations (1, 10, 100, and 1000 ng/ml), and cytotoxicity was measured after 48 and 72 hours using an MTT assay. Results: Our findings indicated that MMAE possesses dose- and time-dependent cytotoxic activities against human breast cancer cells. The morphological features of the treated cells were supportive of the cytotoxic activity of MMAE. The results of the MTT assay showed that MMAE has a significant cytotoxicity against MDA-MB-468 and, to a lesser degree, MDA-MB-453 cells. Conclusion: MMAE can be used as a highly cytotoxic payload for development of antibody-drug conjugates against breast cancer. [ABSTRACT FROM AUTHOR]

Antibody-Drug Conjugates (ADCs) and Small Molecule-Drug Conjugates (SMDCs) represent successful examples of targeted drug-delivery technologies for overcoming unwanted side effects of conventional chemotherapy in cancer treatment. In both strategies, a cytotoxic payload is connected to the tumor homing moiety through a linker that releases the drug inside or in proximity of the tumor cell, and that represents a key component for the final therapeutic effect of the conjugate. Here, we show that the replacement of the Val-Ala- p -aminobenzyloxycarbamate linker with the Gly-Pro-Leu-Gly- p -aminobenzyloxycarbamate (GPLG-PABC) sequence as enzymatically cleavable linker in the SMDC bearing the cyclo [DKP -iso DGR] α V β 3 integrin ligand as tumor homing moiety and the monomethyl auristatin E (MMAE) as cytotoxic payload led to a 4-fold more potent anti-tumoral effect of the final conjugate on different cancer cell lines. In addition, the synthesized conjugate resulted to be significantly more potent than the free MMAE when tested following the "kiss-and-run" protocol, and the relative potency were clearly consistent with the expression of the α V β 3 integrin receptor in the considered cancer cell lines. In vitro enzymatic cleavage tests showed that the GPLG-PABC linker is cleaved by lysosomal enzymes, and that the released drug is observable already after 15 min of incubation. Although additional data are needed to fully characterize the releasing capacity of GPLG-PABC linker, our findings are of therapeutic significance since we are introducing an alternative to other well-established enzymatically sensitive peptide sequences that might be used in the future for generating more efficient and less toxic drug delivery systems., Competing Interests: LS was employed by the KINETO Lab Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Zambra, Ranđelović, Talarico, Borbély, Svajda, Tóvári, Mező, Bodero, Colombo, Arrigoni, Fasola, Gazzola and Piarulli.)

Systemic mastocytosis is a myeloproliferative neoplasm with varying presentation that is caused by infiltration of neoplastic mast cells into extracutaneous tissues. Cytoreductive therapy is used to control organ dysfunction in aggressive systemic mastocytosis and is sometimes needed for control of severe refractory symptoms in patients with indolent disease. However, current standard cytoreductive agents are limited by their suboptimal degree and duration of response and associated significant toxicities, highlighting the need for novel treatments for systemic mastocytosis. Recent studies have identified CD30 as a therapeutic target in systemic mastocytosis, as CD30 is expressed on a majority of neoplastic mast cells. In this case series, the clinical outcomes of 4 patients with aggressive or indolent systemic mastocytosis treated with the anti-CD30 antibody‐drug conjugate brentuximab vedotin are reported. Two patients showed evidence of a response to treatment with a reduction in disease burden, 1 of which has demonstrated a durable response with ongoing benefit for more than 3 years. Treatment with brentuximab vedotin was well-tolerated with side effects that were effectively managed by dose modifications. The results presented suggest that brentuximab vedotin is active in systemic mastocytosis and can induce durable responses with a manageable toxicity profile. [ABSTRACT FROM AUTHOR]

Background: Antibody-drug conjugates (ADCs) are a promising modality for cancer treatment; however, considering their complicated nature, analytical complexity in understanding their pharmacokinetics and pharmacodynamics in the body presents a significant challenge. Results: Vorsetuzumab maleimidocaproyl valine-citrulline p-aminobenzyloxycarbonyl monomethyl auristatin E was used to develop pretreatment and analytical workflows suitable for ADCs. Monomethyl auristatin E release and drug-to-antibody ratio retention were consistent in mouse plasma but inconsistent in monkey and human plasma. Further, metabolites were species-specific. Microflow-liquid chromatography/high-resolution mass spectrometry (LC-HRMS) resulted in a 4-7-fold improvement in detection sensitivity compared with conventional flow LC-HRMS. Conclusion: Microflow-LC-HRMS can be a useful tool in understanding the complex properties of ADCs in the body from a drug metabolism and pharmacokinetics point of view.

Amphiregulin is a transmembrane protein which, when cleaved by the TACE/ADAM17 protease, releases a soluble epidermal growth factor receptor ligand domain that promotes proliferation of normal and malignant cells. We previously described a rabbit monoclonal antibody, GMF-1A3, that selectively recognizes the cell-associated cleaved amphiregulin epitope. Antibody-drug conjugates had anti-tumor activity against human breast cancer xenografts. Several tumor types express amphiregulin, but evidence for a functional requirement for amphiregulin in these malignancies is limited. By directly evaluating amphiregulin cleavage with immunohistochemistry, GMF-1A3 provides a more direct measure of amphiregulin activity. Using 370 specimens from 10 tumor types (as well as normal controls), we demonstrate that cleaved amphiregulin is widely expressed in solid tumors and is especially common (> 50% of cases) in breast, prostate, liver and lung cancer. As a potential companion diagnostic for this antibody-drug conjugate, this assay allows identification of tumors with high levels of the cleaved amphiregulin target., (© The Author(s) 2022. Published by Oxford University Press on behalf of Antibody Therapeutics. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Cervical cancer is one of the most common gynecological malignancies. At present, cytotoxic chemotherapeutic drugs and immunotherapy are the main therapeutic options for recurrent and metastatic cervical cancer. Tisotumab vedotin is an antibody-drug conjugate (ADC) and a potential novel treatment for cervical carcinoma. Tisotumab vedotin targets tissue factor (TF), which is highly expressed on the surface of cervical cancer cells, by delivering the cytotoxic agent monomethyl auristatin E (MMAE) directly into tumor cells. Currently, the U.S. Food and Drug Administration (FDA) has approved tisotumab vedotin for the treatment of adult female patients with recurrent or metastatic cervical cancer with disease progression on or after chemotherapy. This article reviews the results of preclinical studies and clinical trials of tisotumab vedotin. The findings suggest that tisotumab vedotin can induce clinically significant and long-lasting remission with controllable and tolerable safety in the difficult-to-treat group of cervical cancer patients., (Copyright 2022 Clarivate.)

Antibody-drug conjugates (ADCs) are currently among the most successful and important strategies for treating patients with solid tumors. ADCs are composed of a monoclonal antibody and warhead, which are conjugated via a linker. Currently, monomethyl auristatin E (MMAE) is the most widely applied warhead in the development of ADCs. However, MMAE-based ADCs are generally constructed using the MC-VC-PABC linker, and this design has limited structural diversity and some disadvantages. Accordingly, in this study, we generated three types of novel linker-MMAE (with alterations in the spacer, catabolizing area, and self-immolative compared with MC-VC-PABC-MMAE) in ADCs, termed SCT200-linker-MMAE conjugates, and then evaluated the linker-drug plasma stability and the rate of drug release by cathepsin B. The binding ability, internalization rates, and efficacy of all SCT200-linker-MMAE ADCs were systematically studied, and the expression of apoptosis-associated proteins and the therapeutic efficacies of SCT200-M-2, -C-2, and -C-4 were evaluated. The results showed that the activities of some of these ADCs were increased for epidermal growth factor receptor-positive tumors. Moreover, the novel linkers designed in this study can be linked with other antibodies to treat other types of cancer. Overall, these findings provide important insights into the application of SCT200-based linkers in ADCs. [Display omitted] • We generated three types of novel linkers for ADCs. • The activities of a subset of ADCs were increased for EGFR-positive tumors. • These linkers may be used to conjugate other antibodies to treat various cancers. [ABSTRACT FROM AUTHOR]