In this work, we conceived and developed antibody-drug conjugates (ADCs) that could efficiently release the drug after enzymatic cleavage of the linker moiety by tumoral proteases. The antibody-drug linkers we used are the result of a rational optimization of a previously reported PEGylated linker, PUREBRIGHT® MA-P12-PS, which showed excellent drug loading capacities but lacked an inbuilt drug discharge mechanism, thus limiting the potency of the resulting ADCs. To address this limitation, we chose to incorporate a protease-sensitive trigger into the linker to favor the release of a \"PEGless\" drug inside the tumor cells and, therefore, obtain potent ADCs. Currently, most marketed ADCs are based on the Val-Cit dipeptide followed by a self-immolative spacer for releasing the drug in its unmodified form. Here, we selected two untraditional peptide sequences, a Phe-Gly dipeptide and a Val-Ala-Gly tripeptide and placed one or the other in between the drug on one side (N-terminus) and the rest of the linker, including the PEG moiety, on the other side (C-terminus), without a self-immolative group. We found that both linkers responded to cathepsin B, a reference lysosomal enzyme, and liberated a PEG-free drug catabolite, as desired. We then used the two linkers to generate ADCs based on trastuzumab (a HER2-targeting antibody) and DM1 (a microtubule-targeted cytotoxic agent) with an average drug-to-antibody ratio (DAR) of 4 or 8. The ADCs showed restored cytotoxicity in vitro, which was proportional to the DM1 loading and generally higher for the ADCs bearing Val-Ala-Gly in their structure. In an ovarian cancer model in mice, the DAR 8 ADC based on Val-Ala-Gly behaved better than Kadcyla® (an approved ADC of DAR 3.5 used as control throughout this study), leading to a higher tumor volume reduction and more prolonged median survival. Taken together, our results depict a successful linker optimization process and encourage the application of the Val-Ala-Gly tripeptide as an alternative to other existing protease-sensitive triggers for ADCs.

OBJECTIVE: The mesothelin-targeting antibody-drug conjugate anetumab ravtansine was evaluated in combination with the programmed cell death-1 (PD-1) inhibitor pembrolizumab based on the common expression of mesothelin and reports of activity in mesothelioma.
METHODS: A phase 1 safety run-in of the combination of anetumab ravtansine (6.5 mg/kg iv q3weeks) and pembrolizumab (200 mg, IV q3weeks) was conducted, followed by a phase 2 randomization to the combination or pembrolizumab alone at medical centers across the United States and Canada in the National Cancer Institute\'s Experimental Therapeutics Clinical Trials Network. Patients with pleural mesothelioma that expressed mesothelin and had previously received platinum-based therapy were eligible.
RESULTS: In phase 1 (n = 12) only one dose limiting toxicity was observed and the rules for dose reduction were not met. In phase 2, there was no difference in the confirmed response rates between the combination group (n = 18, 2 partial responses [PR], 11 %) and the pembrolizumab group (n = 17, 1 PR, 6 %; z = -0.5523, p = 0.29116). The median PFS was 12.2 months (95 % CI 5.1-not evaluable [NE]) for the combination, and 3.9 months for pembrolizumab (95 % CI 2.1-NE)(HR=0.55, p = 0.20). Patients with high baseline levels of soluble mesothelin who received anetumab ravtansine had a median PFS of 5 months.
CONCLUSIONS: The numeric difference in PFS between treatment groups was not statistically significant, likely related to a smaller than planned sample size. High levels of soluble mesothelin should potentially be considered to select against the use of mesothelin-targeting therapies in development that are neutralized by soluble mesothelin.

Sacituzumab govitecan (SG), a Trop-2-directed antibody-drug conjugate (ADC), was the first ADC approved for patients with metastatic triple-negative breast cancer (mTNBC) who had received at least two prior lines of therapy for advanced disease. Although SG has shown promising clinical activity in treating brain metastases in both ASCENT randomized trials and real-world analysis, its utility in leptomeningeal carcinomatosis (LC) remains underexplored. We report the diagnostic and therapeutic process of a patient who develops extensive LC from TNBC treated with SG. She presented a clinical response after the first cycle of SG with a PFS of 6 months. This case report highlights the need for further inquiry into the use of SG in LC.

T cell-derived cancers are hallmarked by heterogeneity, aggressiveness, and poor clinical outcomes. Available targeted therapies are severely limited due to a lack of target antigens that allow discrimination of malignant from healthy T cells. Here, we report a novel approach for the treatment of T cell diseases based on targeting the clonally rearranged T cell receptor displayed by the cancerous T cell population. As a proof of concept, we identified an antibody with unique specificity toward a distinct T cell receptor (TCR) and developed antibody-drug conjugates, precisely recognizing and eliminating target T cells while preserving overall T cell repertoire integrity and cellular immunity. Our anti-TCR antibody-drug conjugates demonstrated effective receptor-mediated cell internalization, associated with induction of cancer cell death with strong signs of apoptosis. Furthermore, cell proliferation-inhibiting bystander effects observed on target-negative cells may contribute to the molecules\' anti-tumor properties precluding potential tumor escape mechanisms. To our knowledge, this represents the first anti-TCR antibody-drug conjugate designed as custom-tailored immunotherapy for T cell-driven pathologies.

This case report describes a 16-year-old patient with refractory Hodgkin\'s lymphoma who developed bilateral anterior and intermediate uveitis as an adverse reaction to Brentuximab vedotin (BV). This is a rare case of an ocular adverse reaction potentially related to BV, with symptoms like blurred vision, decreased visual acuity, photophobia, and redness. Potential mechanisms include BV targeting CD30+ T cells in the uveal tissue or an immune response triggered by the microtubule-disrupting agent MMAE within BV. This highlights the need for vigilant monitoring of ocular adverse events in BV-treated patients and further research into their mechanisms and management.

OBJECTIVE: While human epidermal growth factor receptor 2 (HER2) is upregulated in endometrial carcinoma-especially in the p53 aberrant type- conventional anti-HER2 therapy is not typically used for this cancer type. Recently, HER2-targeted antibody-drug conjugates have shown antitumor effects against HER2 low-expressing cancers. Therefore, we analyzed the clinicopathological characteristics of HER2-positive endometrial carcinomas including those with low expression, as well as the prognostic significance of p53 and HER2 co-expression.
METHODS: Immunohistochemistry for HER2 and p53 was performed in 530 patients with endometrial carcinoma; 124 cases (23%) were HER2-positive.
RESULTS: Of the HER2-positive cases, >50% were 1+. A high prevalence of HER2 expression was observed in serous (64%), clear-cell (73%), and mixed (64%) carcinomas. Notably, 19% of endometrioid carcinomas were HER2-positive. HER2 positivity was significantly associated with age ≥60 years, high-grade histological subtype, deep myometrium invasion, stage III/IV, recurrence, and death. Univariate analysis showed that HER2-positive cases had reduced progression-free survival (PFS) (p = 0.007) and overall survival (OS) (p = 0.012). However, after adjusting for stage, HER2 positivity was not associated with survival. In the early stage, co-expression of HER2-positive and p53 aberrant types was associated with shorter PFS (p < 0.001) and OS (p < 0.001) compared with at least one negative result. Multivariate analysis of PFS showed HER2 and p53 co-expression (hazard ratio, 1.891; 95% confidence interval, 1.183-5.971, p = 0.008) as an independent prognostic factor.
CONCLUSIONS: This study presents detailed clinicopathological characteristics and the prognostic impact of HER2-positivity in endometrial carcinomas. HER2-targeted antibody-drug conjugate therapy may be broadly applicable to endometrial carcinoma.

BACKGROUND: Delta-like ligand 3 (DLL3) is highly expressed on the cell surface of small cell lung cancer (SCLC), one of the most lethal malignancies, but minimally or not in normal tissues, making it an attractive target for SCLC. However, none of the DLL3-targeting antibody-drug conjugates (ADCs) have been approved for SCLC therapy yet. We developed DB-1314, the new anti-DLL3 ADC composed of a novel humanized anti-DLL3 monoclonal antibody (DB131401) conjugated with eight molecules of P1021 (topoisomerase I inhibitor), and described its preclinical profiles.
METHODS: The binding epitope for DB131401 and Rovalpituzumab was tested by biolayer interferometry. The binding affinity and specificity of DB-1314 to DLL3 and other homologous proteins were respectively measured by surface plasmon resonance and enzyme-linked immunosorbent assay. Internalization, bystander effects, and antibody-dependent cell-mediated cytotoxicity (ADCC) were assessed by respective assay. DLL3 was quantified by antibodies bound per cell assay and immunohistochemistry. In vitro and in vivo growth inhibition studies were evaluated in SCLC cell lines, and cell line/patient-derived xenograft models. The safety profile was measured in cynomolgus monkeys.
RESULTS: DB-1314 induces potent, durable, and dose-dependent antitumor effects in cells in vitro and in cell/patient-derived xenograft models in vivo. The killing activity of DB-1314 mechanically arises from P1021-induced DNA damage, whereby P1021 is delivered and released within tumor cells through DLL3-specific binding and efficient internalization. Bystander effects and ADCC also contribute to the antitumor activity of DB-1314. DB-1314 displays favorable pharmacokinetic and toxicokinetic profiles in rats and cynomolgus monkeys; besides, DB-1314 is well-tolerated at a dose of up to 60 mg/kg in monkeys.
CONCLUSIONS: These results suggest that DB-1314 may be a candidate ADC targeting DLL3 for the treatment of DLL3-positive SCLC, supporting further evaluation in the clinical setting.

Human trophoblastic cell surface antigen 2 (Trop2) is a glycoprotein, a cellular marker of trophoblastic and stem cells, and a calcium signaling transducer involved in several signaling pathways, leading to the proliferation, invasion, and metastasis of tumors. It is expressed at a low level in normal epithelial cells, but at a high level in many tumors, making it an ideal target for cancer therapy. According to previous literature, Trop2 is broadly expressed in all breast cancer subtypes, especially in triple negative breast cancer (TNBC). Several clinical trials have demonstrated the effectiveness of Trop2-targeted therapy in breast cancer. Sacituzumab govitecan (SG) is a Trop2-targeted antibody-drug conjugate (ADC) that has been approved for the treatment of metastatic TNBC and hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-) breast cancer. This article reviews the structure and function of Trop2, several major Trop2-targeted ADCs, other appealing novel Trop2-targeted agents and relevant clinical trials to provide a landscape of how Trop2-targeted treatments will develop in the future.

UNASSIGNED: Treatment of recurrent platinum-resistant high grade serous ovarian cancer (HGSOC) remains a challenge. Novel treatment options for recurrent disease are an unmet need.
UNASSIGNED: A 69-year-old with recurrent, metastatic, platinum-resistant HGSOC overexpressing TROP2 experienced a significant response to the antibody-drug conjugate (ADC) sacituzumab govitecan after multiple failed lines of chemotherapy and targeted treatment. Following sacituzumab govitecan treatment she experienced a confirmed partial response as well as a return of CA-125 to baseline. Having now completed 8 cycles (ie, over 6 months of treatment), her disease continues to demonstrate a response to sacituzumab govitecan treatment. The ADC has been well tolerated at a dose of 10 mg/kg with no dose-limiting toxicity or need for dose reductions.
UNASSIGNED: Sacituzumab govitecan may represent a treatment option for platinum-resistant/recurrent HGSOC that have previously failed prior lines of chemotherapy. Clinical trials with sacituzumab govitecan in platinum-resistant ovarian cancer patients are currently ongoing (https://classic.clinicaltrials.gov/ct2/show/NCT06028932).

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the alimentary tract. The prognosis depends on the primary site, and small intestinal GISTs have a worse prognosis than gastric GISTs. Molecularly targeted drugs to inhibit tyrosine kinase activity of KIT were used for unresectable or recurrent GISTs. However, secondary resistance to the drugs is often acquired, and treatments based on other mechanisms are needed. Previously, we reported that cell adhesion molecule 1 (CADM1) was highly expressed in most of small intestinal GISTs but not in most of gastric GISTs. In the present study, we examined whether the antibody-drug conjugate (ADC) with anti-CADM1 antibody and monomethyl auristatin E (anti-CAD-ADC) shows anti-tumor effect on CADM1-expressing human GIST cells. The ADC adhibited in this study was previously used for CADM1-expressing human mesothelioma cells and showed anti-tumor effect for them in vitro. GIST-T1 cell line of gastric origin which scarcely expresses CADM1 and GIST-T1 cells transfected with CADM1 cDNA (GIST-T1-CAD cells) which highly expresses CADM1 and represents small intestinal GIST were used. In vitro, anti-CAD-ADC showed remarkable cytotoxic activity on GIST-T1-CAD cells, but control ADC did not. Both anti-CAD-ADC and control ADC did not show anti-tumor effect on original GIST-T1 cells. When GIST-T1-CAD cells were subcutaneously injected to the nude mice, intravenous administration of anti-CAD-ADC showed inhibitory effect for tumor enlargement. Tumor of GIST-T1 cells grew even after anti-CAD-ADC injection. When GIST-T1-CAD cells were injected into peritoneal cavity of the SCID mice, intraperitoneal administration of anti-CAD-ADC showed reduction of the peritoneal tumor. On the other hand, peritoneal tumor grew after control ADC administration. Tissue and organ damage due to administration of anti-CAD-ADC was not apparent by macroscopic and histological examinations in mice. These results indicate that anti-CAD-ADC could have apparent anti-tumor effect on CADM1-expressing human GIST cells both in in vitro and in vivo mouse models.