Treating Bladder Cancer: Engineering of Current and Next Generation Antibody-, Fusion Protein-, mRNA-, Cell- and Viral-Based Therapeutics

Abstract

Bladder cancer is a frequent malignancy and has a clinical need for new therapeutic approaches. Antibody and protein technologies came a long way in recent years and new engineering approaches were applied to generate innovative therapeutic entities with novel mechanisms of action. Furthermore, mRNA-based pharmaceuticals recently reached the market and CAR-T cells and viral-based gene therapy remain a major focus of biomedical research. This review focuses on the engineering of biologics, particularly therapeutic antibodies and their application in preclinical development and clinical trials, as well as approved monoclonal antibodies for the treatment of bladder cancer. Besides, newly emerging entities in the realm of bladder cancer like mRNA, gene therapy or cell-based therapeutics are discussed and evaluated. As many discussed molecules exhibit unique mechanisms of action based on innovative protein engineering, they reflect the next generation of cancer drugs. This review will shed light on the engineering strategies applied to develop these next generation treatments and provides deeper insights into their preclinical profiles, clinical stages, and ongoing trials. Furthermore, the distribution and expression of the targeted antigens and the intended mechanisms of action are elucidated.

Keywords: ADC; antibody engineering; bladder cancer; immuno-oncology; immunotherapy; protein engineering; recombinant viral vector vaccines; urothelial carcinoma.

Figure 1

Anatomical illustration of different bladder cancer stages. The bladder as a whole, as well as a zoomed-in illustration of the bladder wall is shown. Different tumors in different tumor stages are illustrated as well as their invasion into the muscle tissue. While Ta, Tis, and T1 are defined as non-muscle-invasive, muscle-invasive bladder cancer (MIBC) disease begins with T2. After penetrating the muscle and reaching the fatty tissue, the T3 stage is reached, where T4 is characterized as growth of the tumor into other organs or metastasizing. Created with BioRender.com.

Figure 2

Mechanisms of action of immune and viral therapies for bladder cancer. (A) T cells can recognize cancer cells via the interaction of their T cell receptor (TCR) with the major histocompatibility complex (MHC) on the target cell, resulting in cytotoxic activity eventually leading to cell death of the malignant cells. However, a prominent escape mechanism of cancer is the upregulation of checkpoint inhibitors like PD-L1, inhibiting cancer-specific T cells from attacking the malignant cells. By blocking the interaction of PD-1 on T cells with its ligand PD-L1 on the tumor cell, T cells are reactivated and can effectively target the tumor. (B) Bispecific T cell engagers (BiTEs) consist of two binding arms, simultaneously binding to a tumor-associated antigen on the tumor cell and CD3, a part of the TCR complex, on T cells, generating a synthetic immunological synapse. This results in T cell activation, eventually leading to the induction of a cytotoxic effect against the targeted tumor cell. (C) Upon binding of Enfortumab Vedotin to nectin-4, the antibody-drug-conjugate (ADC) gets subsequently internalized into the endosome. Next, the complex is transported to the lysosome, where the ADC is degraded. The valine-citrulline linker is cleaved by cathepsin B resulting in the release of monomethyl auristatin E (MMAE) and the subsequent inhibition of the microtubule, eventually leading to cell death. (D) The rAd-IFN/Syn-3 adenovirus is internalized into cells of the bladder after prior instillation. The genetic information of the virus is translocated into the nucleus and upon transduction, these cells produce and secrete IFNα, resulting in an anti-tumor response by activating nearby immune cells. Created with BioRender.com.

Figure 3

Overview of antibody-, protein-, mRNA-, cell- and viral-based drugs that are approved or are in (pre-)clinical development for the treatment of bladder cancer. The molecules belonging to one drug class are marked in the same color. A schematic representation of the molecular architecture is given. Created with BioRender.com.

Figure 4

Cytotoxic payloads and conjugation strategies of approved and clinical-stage antibody-drug-conjugates (ADCs) for the treatment of bladder cancer. On the left, a human IgG1 antibody is shown, where cysteine (yellow) and lysine residues (red) are highlighted, the glycosylation is marked in green, while the light chains are depicted in blue. The heavy chain is illustrated in grey. Depending on the conjugation strategy, either cysteine residues or lysine residues are modified with the toxins illustrated on the right side. Except for ado-Trastuzumab Emtansine, all clinical-stage ADCs for bladder cancer are based on the partial reduction of inter-chain disulfide bonds (yellow), resulting in a maximal drug to antibody ratio (DAR) of 8, while simultaneously reducing the number of potential ADC variants. In ado-Trastuzumab Emtansine conjugation is achieved by coupling to lysine residues (red). The respective linkers and toxins of the payloads are color-coded and named separately. SMCC, succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate; DM1, maytansine; MC, maleimidocaproyl; PAB, p-aminobenzyl; MMAE, monomethyl auristatin E; PEG, polyethylene glycol.