A Phase I Study of Acapatamab, a Half-life Extended, PSMA-Targeting Bispecific T-cell Engager for Metastatic Castration-Resistant Prostate Cancer

PURPOSE

Safety and efficacy of acapatamab, a prostate-specific membrane antigen (PSMA) x CD3 bispecific T-cell engager were evaluated in a first-in-human study in metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

Patients with mCRPC refractory to androgen receptor pathway inhibitor therapy and taxane-based chemotherapy received target acapatamab doses ranging from 0.003 to 0.9 mg in dose exploration (seven dose levels) and 0.3 mg (recommended phase II dose) in dose expansion intravenously every 2 weeks. Safety (primary objective), pharmacokinetics, and antitumor activity (secondary objectives) were assessed.

RESULTS

In all, 133 patients (dose exploration, n = 77; dose expansion, n = 56) received acapatamab. Cytokine release syndrome (CRS) was the most common treatment-emergent adverse event seen in 97.4% and 98.2% of patients in dose exploration and dose expansion, respectively; grade ≥ 3 was seen in 23.4% and 16.1%, respectively. Most CRS events were seen in treatment cycle 1; incidence and severity decreased at/beyond cycle 2. In dose expansion, confirmed prostate-specific antigen (PSA) responses (PSA50) were seen in 30.4% of patients and radiographic partial responses in 7.4% (Response Evaluation Criteria in Solid Tumors 1.1). Median PSA progression-free survival (PFS) was 3.3 months [95% confidence interval (CI): 3.0-4.9], radiographic PFS per Prostate Cancer Clinical Trials Working Group 3 was 3.7 months (95% CI: 2.0-5.4). Acapatamab induced T-cell activation and increased cytokine production several-fold within 24 hours of initiation. Treatment-emergent antidrug antibodies were detected in 55% and impacted serum exposures in 36% of patients in dose expansion.

CONCLUSIONS

Acapatamab was safe and tolerated and had a manageable CRS profile. Preliminary signs of efficacy with limited durable antitumor activity were observed. Acapatamab demonstrated pharmacokinetic and pharmacodynamic activity.

FDA-Approved Chimeric Antigen Receptor (CAR)-T Cell Therapy for Different Cancers-A Recent Perspective

Cancer is one of the most prevalent diseases in the world, and their rate of occurence has been increased in recent decades. Current review article, summarizes the novel treatment options Chimeric Antigen Receptor-T (CAR-T) cell therapy for various cancers constitute a major health and development challenge, impacting every aspect of sustainable development quoted by goal 3 good health and well-being of UN sustainable goals. WHO estimates that 70% of cancer deaths occur in low- and middle- income countries (LMICs) by 2030, LMICs are expected to bear the brunt of the expected 24.1 million new cancer cases per year. This current review article focuses and discussed about CAR-T cell therapy for various cancers against most prevalent non-communicable disease cancer disease stipulated by WHO and UN sustainable goals. Three literature databases Google scholar, Science Direct, PubMed was utilized to search and collect CAR-T cell treatment options for different cancers published articles sources in between January 2000 and December 2023. There were a total of 18,700 papers found, with 48 of them being found to be eligible focusing various cancer treatment by CAR-T cells utilized for the study. Based on the information gathered, CAR-T cell therapy treating different cancers and their merit and its advantages in heal and improve certain cancers was also discussed in this review article with their detailed molecular mechanisms. This article also gives an insight to utilize CAR-T cell treatment protocols for rejuvenating cancer patient from such ruthless cancer disease condition thereby improving life span of cancer patients and eradication of disease in some cases.

Emerging Immunotherapy Approaches for Treating Prostate Cancer

Immunotherapy has emerged as an important approach for cancer treatment, but its clinical efficacy has been limited in prostate cancer compared to other malignancies. This review summarizes key immunotherapy strategies under evaluation for prostate cancer, including immune checkpoint inhibitors, bispecific T cell-engaging antibodies, chimeric antigen receptor (CAR) T cells, therapeutic vaccines, and cytokines. For each modality, the rationale stemming from preclinical studies is discussed along with outcomes from completed clinical trials and strategies to improve clinical efficacy that are being tested in ongoing clinical trials. Imperative endeavors include biomarker discovery for patient selection, deciphering resistance mechanisms, refining cellular therapies such as CAR T cells, and early-stage intervention were reviewed. These ongoing efforts instill optimism that immunotherapy may eventually deliver significant clinical benefits and expand treatment options for patients with advanced prostate cancer.

Bispecific T-Cell Engagers Therapies in Solid Tumors: Focusing on Prostate Cancer

Over the past decade, immunotherapy has demonstrated an impressive improvement in treatment outcomes for multiple cancers. Following the landmark approvals for use of immune checkpoint inhibitors, new challenges emerged in various clinical settings. Not all tumor types harbor immunogenic characteristics capable of triggering responses. Similarly, many tumors' immune microenvironment allows them to become evasive, leading to resistance and, thus, limiting the durability of responses. To overcome this limitation, new T-cell redirecting strategies such as bispecific T-cell engager (BiTE) have become attractive and promising immunotherapies. Our review provides a comprehensive perspective of the current evidence of BiTE therapies in solid tumors. Considering that immunotherapy has shown modest results in advanced prostate cancer to date, we review the biologic rationale and promising results of BiTE therapy in this clinical setting and discuss potential tumor-associated antigens that may be integrated into BiTE construct designs. Our review also aims to evaluate the advances of BiTE therapies in prostate cancer, illustrate the major obstacles and underlying limitations, and discuss directions for future research.

Current and upcoming radionuclide therapies in the direction of precision oncology: A narrative review

As new molecular tracers are identified to target specific receptors, tissue, and tumor types, opportunities arise for the development of both diagnostic tracers and their therapeutic counterparts, termed "theranostics." While diagnostic tracers utilize positron emitters or gamma-emitting radionuclides, their theranostic counterparts are typically bound to beta and alpha emitters, which can deliver specific and localized radiation to targets with minimal collateral damage to uninvolved surrounding structures. This is an exciting time in molecular imaging and therapy and a step towards personalized and precise medicine in which patients who were either without treatment options or not candidates for other therapies now have expanded options, with tangible data showing improved outcomes. This manuscript explores the current state of theranostics, providing background, treatment specifics, and toxicities, and discusses future potential trends.

Bispecific PSMA antibodies and CAR-T in metastatic castration-resistant prostate cancer

Prostate cancer is the most common cancer among men and the second leading cause of cancer-related deaths in men in the United States. The treatment paradigm for prostate cancer has evolved with the emergence of a variety of novel therapies which have improved survival; however, treatment-related toxicities are abundant and durable responses remain rare. Immune checkpoint inhibitors have shown modest activity in a small subset of patients with prostate cancer and have not had an impact on most men with advanced disease. The discovery of prostate-specific membrane antigen (PSMA) and the understanding of its specificity to prostate cancer has identified it as an ideal tumor-associated antigen and has revived the enthusiasm for immunotherapeutics in prostate cancer. T-cell immunotherapy in the form of bispecific T-cell engagers (BiTEs) and chimeric antigen receptor (CAR) T-cell therapy have shown exceptional success in treating various hematologic malignancies, and are now being tested in patients with prostate cancer with drug design centered on various target ligands including not just PSMA, but others as well including six-transmembrane epithelial antigen of the prostate 1 (STEAP1) and prostate stem cell antigen (PSCA). This summative review will focus on the data surrounding PSMA-targeting T-cell therapies. Early clinical studies with both classes of T-cell redirecting therapies have demonstrated antitumor activity; however, there are multiple challenges with this class of agents, including dose-limiting toxicity, 'on-target, off-tumor' immune-related toxicity, and difficulty in maintaining sustained immune responses within a complex and overtly immunosuppressive tumor microenvironment. Reflecting on experiences from recent trials has been key toward understanding mechanisms of immune escape and limitations in developing these drugs in prostate cancer. Newer generation BiTE and CAR T-cell constructs, either alone or as part of combination therapy, are currently under investigation with modifications in drug design to overcome these barriers. Ongoing innovation in drug development will likely foster successful implementation of T-cell immunotherapy bringing transformational change to the treatment of prostate cancer.

Chimeric Antigen Receptor T-Cells: An Overview of Concepts, Applications, Limitations, and Proposed Solutions

Adaptive immunity, orchestrated by B-cells and T-cells, plays a crucial role in protecting the body from pathogenic invaders and can be used as tools to enhance the body's defense mechanisms against cancer by genetically engineering these immune cells. Several strategies have been identified for cancer treatment and evaluated for their efficacy against other diseases such as autoimmune and infectious diseases. One of the most advanced technologies is chimeric antigen receptor (CAR) T-cell therapy, a pioneering therapy in the oncology field. Successful clinical trials have resulted in the approval of six CAR-T cell products by the Food and Drug Administration for the treatment of hematological malignancies. However, there have been various obstacles that limit the use of CAR T-cell therapy as the first line of defense mechanism against cancer. Various innovative CAR-T cell therapeutic designs have been evaluated in preclinical and clinical trial settings and have demonstrated much potential for development. Such trials testing the suitability of CARs against solid tumors and HIV are showing promising results. In addition, new solutions have been proposed to overcome the limitations of this therapy. This review provides an overview of the current knowledge regarding this novel technology, including CAR T-cell structure, different applications, limitations, and proposed solutions.

Novel immune engagers and cellular therapies for metastatic castration-resistant prostate cancer: do we take a BiTe or ride BiKEs, TriKEs, and CARs?

BACKGROUND

Checkpoint inhibitors and currently approved cellular products for metastatic castration-resistant prostate cancer have not resulted in revolutionary changes in outcomes compared to other solid tumors. Much of this lack of progress is attributed to the unique tumor microenvironment of prostate cancer that is often immunologically cold and immunosuppressive. These unique conditions emphasize the need for novel therapeutic options. In this review, we will discuss progress made in design of T- and NK cell immune engagers in addition to chimeric antigen receptor products specifically designed for prostate cancer that are currently under investigation in clinical trials.

METHODS

We searched peer-reviewed literature on the PubMed and the ClinicalTrials.gov databases for active clinical trials using the terms "bispecific T-cell engager," "bispecific killer engager," "trispecific killer engager," "chimeric antigen receptor," "metastatic castration-resistant prostate cancer," and "neuroendocrine prostate cancer."

RESULTS

Ten bispecific T-cell engager studies and nine chimeric antigen receptor-based products were found. Published data were compiled and presented based on therapeutic class.

CONCLUSIONS

Multiple immune engagers and cell therapies are in the development pipeline and demonstrate promise to address barriers to better outcomes for metastatic castration-resistant prostate cancer patients.

Mesothelin/CD3 half-life extended bispecific T-cell engager molecule shows specific tumor uptake and distributes to mesothelin and CD3 expressing tissues

BiTE ® (bispecific T-cell engager) molecules exert antitumor activity by binding one arm to CD3 on cytotoxic T-cells and the other arm to a tumor-associated antigen. We generated a fully mouse cross-reactive mesothelin (MSLN)-targeted BiTE molecule that is genetically fused to a Fc-domain for half-life extension, and evaluated biodistribution and tumor targeting of a zirconium-89 (89Zr)-labeled MSLN HLE BiTE molecule in 4T1 breast cancer bearing syngeneic mice with positron emission tomography (PET). Biodistribution of 50 µg 89Zr-MLSN HLE BiTE was studied over time by PET imaging in BALB/c mice and revealed uptake in tumor and lymphoid tissues with an elimination half-life of 63.4 hours. Compared to a non-targeting 89Zr-control HLE BiTE, the 89Zr-MLSN HLE BiTE showed a 2-fold higher tumor uptake and higher uptake in lymphoid tissues. Uptake in the tumor colocalized with mesothelin expression, while uptake in the spleen colocalized with CD3 expression. Evaluation of the effect of protein doses on the biodistribution and tumor targeting of 89Zr-MSLN HLE BiTE revealed for all dose groups that uptake in the spleen was faster than in the tumor (day 1 vs day 5). The lowest dose of 10 µg 89Zr-MSLN HLE BiTE had higher spleen uptake and faster blood clearance compared to higher doses of 50 µg and 200 µg. 89Zr-MSLN HLE BiTE tumor uptake was similar at all doses. Conclusion: The MSLN HLE BiTE showed specific tumor uptake and both arms contributed to the biodistribution profile. These findings support the potential for clinical translation of HLE BiTE molecules.

Changing the History of Prostate Cancer with New Targeted Therapies

The therapeutic landscape of metastatic castration-resistant prostate cancer (mCRPC) is changing due to the emergence of new targeted therapies for the treatment of different molecular subtypes. Some biomarkers are described as potential molecular targets different from classic androgen receptors (AR). Approximately 20–25% of mCRPCs have somatic or germline alterations in DNA repair genes involved in homologous recombination. These subtypes are usually associated with more aggressive disease. Inhibitors of the enzyme poly ADP ribose polymerase (PARPi) have demonstrated an important benefit in the treatment of these subtypes of tumors. However, tumors that resistant to PARPi and wildtype BRCA tumors do not benefit from these therapies. Recent studies are exploring drug combinations with phosphatidylinositol-3-kinase (PI3K) or protein kinase B (AKT) inhibitors, as mechanisms to overcome resistance or to induce BRCAness and synthetic lethality. This article reviews various different novel strategies to improve outcomes in patients with prostate cancer.

Refining Immuno-Oncology Approaches in Metastatic Prostate Cancer: Transcending Current Limitations

OPINION STATEMENT

Due to its immunosuppressive tumor microenvironment, prostate cancer has historically been difficult to treat with immuno-oncology approaches. Other than pembrolizumab, which is now regulatory-approved for all microsatellite instability (MSI)-high and tumor mutational burden (TMB)-high advanced solid tumors, sipuleucel-T is the only immunotherapeutic agent approved by the US Food and Drug Administration (FDA) for prostate cancer. However, sipuleucel-T efficacy is optimal for select patients with indolent metastatic castration-resistant prostate cancer. Although manipulation of immune regulation by blocking immune checkpoints has led to substantial benefit in many cancers, experience with single-agent CTLA-4 and PD-1 or PD-L1 antibodies has shown limited effect for the majority of patients with prostate cancer, especially when administered as monotherapy. Combination therapies are now being attempted, in addition to enrichment strategies employing patient clinicopathologic and biologic characteristics that may heighten responses to immuno-oncology treatment, such as PD-L1 expression, TMB, MSI status, and alterations in CDK12. More work is needed to overcome the immune-exclusive barriers in prostate cancer, such as relatively low TMB, increased activity of myeloid-derived suppressor cells (MDSCs) and regulatory T cells, and defects in major histocompatibility complex (MHC) class I expression and interferon (IFN)-1 signaling. A promising approach and the likely next step in immuno-oncology for prostate cancer involves forced direction to markers expressed by prostate cancer tumor cells, such as prostate-specific membrane antigen (PSMA), that bypass the typical requirements for MHC class I interaction. The future will incorporate bispecific antibodies and chimeric antigen receptor (CAR)-T cells, potentially targeted towards phenotypic markers identified by next-generation PET imaging as part of the next wave of "precision medicine" in prostate cancer. Ultimately, we believe that the immune-exclusive prostate cancer tumor microenvironment can be overcome, and that patient outcomes can be enhanced through these more refined immuno-oncology approaches.

Management of men with metastatic castration-resistant prostate cancer following potent androgen receptor inhibition: a review of novel investigational therapies

BACKGROUND

Androgen-targeted therapy and chemotherapy are currently the mainstay of treatment in metastatic castration resistant prostate cancer (mCRPC). When progression occurs despite these therapeutic strategies, additional FDA-approved treatment options are lacking. However, there is a vast amount of emerging data surrounding novel investigational therapies in this space.

METHODS

We reviewed and summarized the body of literature surrounding the current treatment options for mCRPC. Medline and Pubmed as well as abstracts from international congresses were utilized to gather relevant literature surrounding investigational treatment of mCRPC. We highlight the results of recent trials investigating the use of novel strategies to treat mCRPC.

RESULTS

Androgen-targeted therapy and chemotherapy will remain foundational in the treatment of mCRPC. However, heavily pretreated patients who have developed resistance may benefit from novel therapeutic strategies. The use of poly(adenosine diphosphate [ADP]-ribose) polymerase inhibitors (PARPi) has now gained FDA approval for patients with homologous recombination repair (HRR) gene mutations. Novel androgen receptor (AR) degraders and the use of radioligand therapy (RLT) with Lu-PSMA-617 (Lu-PSMA) are under investigation. Immune-directed therapies, including programmed death (PD-1) inhibition, bi-specific T-cell engager (BiTE) technology, and chimeric antigen receptor (CAR) T-cell therapy, have shown promise in early phase trials. Further understanding of resistance mechanisms has led to additional therapeutic targets, including targeting the PI3K-Akt-mTOR pathway and enhancer of zester homolog 2 (EZH2).

CONCLUSIONS

Based on our review of the literature, exciting new therapeutic strategies exist for the treatment of mCRPC. In particular, PARPi, AR degraders, PSMA-targeted therapies, immune-directed therapies, and agents targeting resistance mechanisms as monotherapy or in combination could improve patient outcomes. Additional data from randomized trials are necessary to understand the efficacy and tolerability of these treatment strategies.

Immunotherapy for Metastatic Prostate Cancer: Current and Emerging Treatment Options

The advent of immunotherapy has revolutionized cancer treatment. Prostate cancer has an immunosuppressive microenvironment and a low tumor mutation burden, resulting in low neoantigen expression. The consensus was that immunotherapy would be less effective in prostate cancer. However, recent studies have reported that prostate cancer does have a high number of DNA damage and repair gene defects. Immunotherapies that have been tested in prostate cancer so far have been mainly vaccines and checkpoint inhibitors. A combination of genomically targeted therapies, with approaches to alleviate immune response and thereby make the tumor microenvironment immunologically hot, is promising.

PSMA Theranostics: Review of the Current Status of PSMA-Targeted Imaging and Radioligand Therapy

Prostate-specific membrane antigen (PSMA) has been the subject of extensive investigation in the past two decades as a promising molecular target for prostate cancer (PCa). Its appealing molecular features have enabled the development of a novel diagnostic and therapeutic-thus "theranostic"-approach to PCa. There is now substantial evidence of the high sensitivity of PSMA-targeted imaging for PCa lesions and growing evidence of the therapeutic efficacy of PSMA radioligand therapy for metastatic castration-resistant prostate cancer. This article presents a broad overview of the current status of PSMA theranostics, including current evidence, potential clinical impact, and active areas of research.

The BiTE (bispecific T-cell engager) platform: Development and future potential of a targeted immuno-oncology therapy across tumor types

Immuno-oncology therapies engage the immune system to treat cancer. BiTE (bispecific T-cell engager) technology is a targeted immuno-oncology platform that connects patients' own T cells to malignant cells. The modular nature of BiTE technology facilitates the generation of molecules against tumor-specific antigens, allowing off-the-shelf immuno-oncotherapy. Blinatumomab was the first approved canonical BiTE molecule and targets CD19 surface antigens on B cells, making blinatumomab largely independent of genetic alterations or intracellular escape mechanisms. Additional BiTE molecules in development target other hematologic malignancies (eg, multiple myeloma, acute myeloid leukemia, and B-cell non-Hodgkin lymphoma) and solid tumors (eg, prostate cancer, glioblastoma, gastric cancer, and small-cell lung cancer). BiTE molecules with an extended half-life relative to the canonical BiTE molecules are also being developed. Advances in immuno-oncology made with BiTE technology could substantially improve the treatment of hematologic and solid tumors and offer enhanced activity in combination with other treatments.

Immunotherapy for castration-resistant prostate cancer: has its time arrived?

Introduction: Within the last decade, multiple innovative immune platforms have been developed and tested in patients with metastatic castration-resistant prostate cancer (mCRPC) with only one demonstrating a survival benefit. The advent of immunogenomics along with the availability of diverse checkpoint inhibitors provides inroads in treating these patients, in many cases with significant clinical impact but unfortunately not in all patients. How to exploit these novel platforms remains an area of increased interest especially in the setting of new agents that can affect the tumor microenvironment and potentially render a 'cold' tumor to become 'hot.'Areas covered: This review highlights the current changes and challenges in this field and how to best use our current knowledge for better trial designs in patients with mCRPC.Expert opinion: Recent understanding of the inhibitory milieu within the tumor microenvironment has fostered the use of combinatorial strategies that target not only tumor cells but capitalize on controlling inhibitory cell populations and cytokines that induce a hostile setting for immune cells. Immunogenomics and genomic interrogation of prostate cancers have opened a vista as to how patients' tumors that can respond to immune agents that previously were thought have minimal antitumor activity.

CAR-T cell therapy: a potential new strategy against prostate cancer

Prostate cancer (PCa) is one of the main causes of cancer-related death in men. In the present immunotherapy era, several immunotherapeutic agents have been evaluated in PCa with poor results, possibly due to its low mutational burden. The recent development of chimeric antigen receptor (CAR)-T cell therapy redirected against cancer-specific antigens would seem to provide the means for bypassing immune tolerance mechanisms. CAR-T cell therapy has proven effective in eradicating hematologic malignancies and the challenge now is to obtain the same degree of in solid tumors, including PCa. In this study we review the principles that have guided the engineering of CAR-T cells and the specific prostatic antigens identified as possible targets for immunological and non-immunological therapies. We also provide a state-of-the-art overview of CAR-T cell therapy in PCa, defining the key obstacles to its development and underlining the mechanisms used to overcome these barriers. At present, although there are still many unanswered questions regarding CAR-T cell therapy, there is no doubt that it has the potential to become an important treatment option for urological malignancies.