Hexavalent TRAIL Fusion Protein Eftozanermin Alfa Optimally Clusters Apoptosis-Inducing TRAIL Receptors to Induce On-Target Antitumor Activity in Solid Tumors

A bispecific anti-MUC16/anti-death receptor 5 antibody achieves effective and tumor-selective death receptor 5-mediated tumor regression

The bispecific antibody IMV-M was designed to selectively bind and cluster death receptor 5 (DR5) upon engaging the tumor antigen MUC16 through a novel mechanism-clustering multiple IMV-M molecules on a single MUC16 molecule. IMV-M demonstrated potent, MUC16-selective anti-tumor activity in vitro and in xenograft models without requiring secondary crosslinking, and a pilot non-human primate toxicity study detected no toxicity. Our findings suggest that antibody clustering effectively induces DR5 clustering, resulting in anti-tumor activity. Unlike anti-MUC16 antibody-drug conjugates (ADCs), which rely on cytotoxic payloads, this approach offers a safer and more effective therapeutic strategy. Notably, MUC16 is overexpressed in substantial subsets of ovarian, pancreatic, and lung cancers, with minimal expression in normal tissues, suggesting the broad applicability of this bispecific antibody.

Advances in the study of death receptor 5

DR5, a receptor with the highest affinity for TRAIL under physiological conditions, selectively induces apoptosis in specific target cells such as tumor and aberrant immune cells, while minimally affecting normal cells. The TRAIL-DR5 signaling pathway is a crucial regulatory mechanism when the body responds to various exogenous interference factors, including viruses, chemicals, and radiation. This pathway plays a vital role in maintaining physiological homeostasis and in the pathological development of various diseases. Different modulations of DR5, such as upregulation, activation, and antagonism, hold significant potential for therapeutic applications in tumors, cardiovascular diseases, autoimmune diseases, viral infections, and radiation injuries. This article provides an overview of the current research progress on DR5, including the status and prospects of its clinical applications.

Turn TRAIL Into Better Anticancer Therapeutic Through TRAIL Fusion Proteins

BACKGROUND

TNF-related apoptosis-inducing ligand (TRAIL) belongs to the tumor necrosis factor superfamily. TRAIL selectively induces apoptosis in tumor cells while sparing normal cells, which makes it an attractive candidate for cancer therapy. Recombinant soluble TRAIL and agonistic antibodies against TRAIL receptors have demonstrated safety and tolerability in clinical trials. However, they have failed to exhibit expected clinical efficacy. Consequently, extensive research has focused on optimizing TRAIL-based therapies, with one of the most common approaches being the construction of TRAIL fusion proteins.

METHODS

An extensive literature search was conducted to identify studies published over the past three decades related to TRAIL fusion proteins. These various TRAIL fusion strategies were categorized based on their effects achieved.

RESULTS

The main fusion strategies for TRAIL include: 1. Construction of stable TRAIL trimers; 2. Enhancing the polymerization capacity of soluble TRAIL; 3. Increasing the accumulation of TRAIL at tumor sites by fusing with antibody fragments or peptides; 4. Decorating immune cells with TRAIL; 5. Prolonging the half-life of TRAIL in vivo; 6. Sensitizing cancer cells to overcome resistance to TRAIL treatment.

CONCLUSION

This work focuses on the progress in recombinant TRAIL fusion proteins and aims to provide more rational and effective fusion strategies to enhance the efficacy of recombinant soluble TRAIL, facilitating its translation from bench to bedside as an effective anti-cancer therapeutic.

The Innate Immune System and the TRAIL-Bcl-XL Axis Mediate a Sex Bias in Lung Cancer and Confer a Therapeutic Vulnerability in Females

There is a significant sex bias in lung cancer, with males showing increased mortality compared with females. A better mechanistic understanding of these differences could help identify therapeutic targets to personalize cancer therapies to each sex. After observing a clear sex bias in humanized mice, with male patient-derived xenograft lung tumors being more progressive and deadlier than female patient-derived xenograft lung tumors, we identified mouse tumor models of lung cancer with the same sex bias. This sex bias was not observed in models of breast, colon, melanoma, and renal cancers. In vivo, the sex bias in growth and lethality required intact ovaries, functional innate NK cells and monocytes/macrophages, and the activating receptor NKG2D. Ex vivo cell culture models were sensitized to the anticancer effects of NKG2D-mediated NK cell and macrophage killing through the TRAIL-Bcl-XL axis when cultured with serum from female mice with intact ovaries. In both flank and orthotopic models, the Bcl-XL inhibitor navitoclax (ABT-263) improved tumor growth control in female mice and required NK cells, macrophages, and the TRAIL signaling pathway. This research suggests that navitoclax and TRAIL pathway agonists could be used as a personalized therapy to improve outcomes in women with lung cancer. Significance: Lung cancers in females are more susceptible to killing through a TRAIL-Bcl-XL axis, indicating that targeting this axis therapeutically could represent a personalized approach to treat female patients with lung cancer.

Tumor necrosis factor superfamily signaling: life and death in cancer

Immune checkpoint inhibitors have shaped the landscape of cancer treatment. However, many patients either do not respond or suffer from later progression. Numerous proteins can control immune system activity, including multiple tumor necrosis factor (TNF) superfamily (TNFSF) and TNF receptor superfamily (TNFRSF) members; these proteins play a complex role in regulating cell survival and death, cellular differentiation, and immune system activity. Notably, TNFSF/TNFRSF molecules may display either pro-tumoral or anti-tumoral activity, or even both, depending on tumor type. Therefore, TNF is a prototype of an enigmatic two-faced mediator in oncogenesis. To date, multiple anti-TNF agents have been approved and/or included in guidelines for treating autoimmune disorders and immune-related toxicities after immune checkpoint blockade for cancer. A confirmed role for the TNFSF/TNFRSF members in treating cancer has proven more elusive. In this review, we highlight the cancer-relevant TNFSF/TNFRSF family members, focusing on the death domain-containing and co-stimulation members and their signaling pathways, as well as their complicated role in the life and death of cancer cells.

Targeting Death Receptor 5 (DR5) for the imaging and treatment of primary bone and soft tissue tumors: an update of the literature

Background

Death Receptor 5 (DR5) is expressed on the surface of primary bone and soft tissue sarcoma cells, and its activation induces cell death primarily through apoptosis. The combination of DR5 agonists and commonly used chemotherapeutic agents, such as doxorubicin, can promote cell death. Currently, clinical trials are investigating the effectiveness of DR5 activation using new biological agents, such as bi-specific or tetravalent antibodies, in improving the survival of patients with relapsed or refractory cancers. Furthermore, investigations continue into the use of novel combination therapies to enhance DR5 response, for example, with inhibitor of apoptosis protein (IAP) antagonist agents [such as the second mitochondria-derived activator of caspase (SMAC) mimetics] and with immune checkpoint inhibitor anti-programmed death-ligand 1 (anti-PD-L1) or anti-programmed cell death-1 (anti-PD-1) antibodies. Other therapies include nanoparticle-mediated delivery of TRAIL plasmid DNA or TRAIL mRNA and stem cells as a vehicle for the targeted delivery of anti-cancer agents, such as TRAIL, to the tumor.

Methods

Scoping review of the literature from November 2017 to March 2024, utilizing PubMed and Google Scholar.

Results

New agents under investigation include nanoTRAIL, anti-Kv10.1, multimeric IgM, and humanized tetravalent antibodies. Developments have been made to test novel agents, and imaging has been used to detect DR5 in preclinical models and patients. The models include 3D spheroids, genetically modified mouse models, a novel jaw osteosarcoma model, and patient-derived xenograft (PDX) animal models. There are currently two ongoing clinical trials focusing on the activation of DR5, namely, IGM-8444 and INBRX-109, which have progressed to phase 2. Further modifications of TRAIL delivery with fusion to single-chain variable fragments (scFv-TRAIL), directed against tumor-associated antigens (TAAs), and in the use of stem cells focus on targeted TRAIL delivery to cancer cells using bi-functional strategies.

Conclusion

In vitro, in vivo, and clinical trials, as well as advances in imaging and theranostics, indicate that targeting DR5 remains a valid strategy in the treatment of some relapsed and refractory cancers.

Chemical synthetic approaches to mimic the TRAIL: promising cancer therapeutics

Apoptosis is programmed cell death that eliminates undesired cells to maintain homeostasis in metazoan. Aberration of this process may lead to cancer genesis. The tumor necrosis factor related apoptosis inducing ligand (TRAIL) induces apoptosis in cancer cells after ligation with death receptors (DR4/DR5) while sparing most normal cells. Therefore, strategies to induce apoptosis in cancer cells by mimicking the TRAIL emerge as a promising therapeutic tool. Hence, approaches are taken to develop TRAIL/DR-based cancer therapeutics. The recombinant soluble TRAIL (rhTRAIL) and death receptor agonistic antibodies were produced and tested pre-clinically and clinically. Pre-clinical and clinical trial data demonstrate that these therapeutics are safe and relatively well tolerated. But some of these therapeutics failed to exert adequate efficacy in clinical settings. Besides these biotechnologically derived therapeutics, a few chemically synthesized therapeutics are reported. Some of these therapeutics exert considerable efficacy in vitro and in vivo. In this review, we will discuss chemically synthesized TRAIL/DR-based therapeutics, their chemical and biological behaviour, design concepts and strategies that may contribute to further improvement of TRAIL/DR-based therapeutics.

Targeting apoptotic pathways for cancer therapy

Apoptosis is a form of programmed cell death that is mediated by intrinsic and extrinsic pathways. Dysregulation of and resistance to cell death are hallmarks of cancer. For over three decades, the development of therapies to promote treatment of cancer by inducing various cell death modalities, including apoptosis, has been a main goal of clinical oncology. Apoptosis pathways also interact with other signaling mechanisms, such as the p53 signaling pathway and the integrated stress response (ISR) pathway. In addition to agents directly targeting the intrinsic and extrinsic pathway components, anticancer drugs that target the p53 and ISR signaling pathways are actively being developed. In this Review, we discuss selected and promising anticancer therapies in various stages of development, including drug targets, mechanisms, and resistance to related treatments, focusing especially on B cell lymphoma 2 (BCL-2) inhibitors, TRAIL analogues, DR5 antibodies, and strategies that target p53, mutant p53, and the ISR.

Self-Illuminating Nanoagonist Simultaneously Induces Dual Cell Death Pathways via Death Receptor Clustering for Cancer Therapy

Inducing death receptor 5 (DR5) clustering holds particular promise in tumor-specific therapeutics because it could trigger an apoptotic cascade in cancerous cells. Herein, we present a tumor microenvironment H2O2-responsive self-illuminating nanoagonist, which could induce dual tumor cell death pathways through enhancing DR5 clustering. By conjugating DR5 ligand peptides onto the surfaces of self-illuminating nanoparticles with cross-linking capacity, this strategy not only provides scaffolds for ligands to bind receptors but also cross-links them through photo-cross-linking. This strategy allows for efficient activation of DR5 downstream signaling, initiating the extrinsic apoptosis pathway and immunogenic cell death of tumor cells, and contributes to improved tumor-specific immune responses, resulting in enhanced antitumor efficacy and minimized systemic adverse effects.

Pharmacokinetics and immunogenicity of eftozanermin alfa in subjects with previously-treated solid tumors or hematologic malignancies: results from a phase 1 first-in-human study

PURPOSE

Eftozanermin alfa is a second-generation tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor agonist that enhances death receptor 4/5 clustering on tumor cells to induce apoptosis. We report the pharmacokinetics and immunogenicity of eftozanermin alfa administered intravenously to 153 adults with previously-treated solid tumors or hematologic malignancies from the first-in-human, open-label, dose-escalation and dose-optimization study.

METHODS

Dose escalation evaluated eftozanermin alfa monotherapy 2.5-15 mg/kg on Day 1 or Days 1/8 of a 21-day cycle. Dose optimization evaluated eftozanermin alfa monotherapy or combination therapy with either oral venetoclax 400-800 mg daily (eftozanermin alfa 1.25-7.5 mg/kg Days 1/8/15 of a 21-day cycle) or chemotherapy (eftozanermin alfa 3.75 or 7.5 mg/kg Days 1/8/15/22 of a 28-day cycle and FOLFIRI regimen [leucovorin, 5-fluorouracil, and irinotecan] with/without bevacizumab on Days 1/15 of a 28-day cycle).

RESULTS

Systemic exposures (maximum observed concentration [Cmax] and area under the concentration-time curve [AUC]) of eftozanermin alfa were approximately dose-proportional across the entire dose escalation range with minimal to no accumulation in Cycle 3 versus Cycle 1 exposures. Comparable exposures and harmonic mean half-lives (35.1 h [solid tumors], 31.3 h [hematologic malignancies]) were observed between malignancy types. Exposures (dose-normalized Cmax and AUC) in Japanese subjects were similar to non-Japanese subjects. Furthermore, eftozanermin alfa/venetoclax combination therapy did not have an impact on the exposures of either agent. Treatment-emergent anti-drug antibodies were observed in 9.4% (13/138) of subjects.

CONCLUSIONS

The study results, including a pharmacokinetic profile consistent with weekly dosing and low incidence of immunogenicity, support further investigation of eftozanermin alfa.

TRIAL REGISTRATION ID

NCT03082209.

A TRAILR2/CDH3 bispecific antibody demonstrates selective apoptosis and tumor regression in CDH3-positive pancreatic cancer

Exploitation of extrinsic apoptosis signaling via TRAILR2 activation represents a promising therapeutic concept in cancer treatment. The limited clinical success of previous TRAILR2 agonistic agents, to date, has been ascribed to either poor efficacy or hepatotoxicity. TR2/CDH3 BAB is a human bispecific antibody that relies on binding both CDH3 and TRAILR2 on cell surfaces to achieve TRAILR2 hyperclustering and efficient apoptosis induction by TRAILR2 signaling selectively in CDH3-expressing tumor cells. We demonstrate target-dependent TR2/CDH3 BAB anti-tumor activity in CRISPR/Cas9-engineered TRAILR2 or CDH3 knock-out cells. By utilizing the cell line screening platform PRISM, we found selective TR2/CDH3 BAB efficacy in various cancer types, such as pancreatic, gastric, colorectal, and triple negative breast cancer. The efficacy of TR2/CDH3 BAB correlated with caspase activation in cancer cell lines and in xenograft tumor tissues. In pancreatic ductal adenocarcinoma (PDAC), where patient benefit from current cytotoxic therapy options is unsatisfactory, a close to uniform cell surface expression of CDH3 and TRAILR2 was observed, which will qualify the majority of PDAC patients for TR2/CDH3 BAB-based treatment. TR2/CDH3 BAB demonstrated anti-tumor activity in a panel of PDAC patient-derived xenograft models, including tumor regressions. By combining TR2/CDH3 BAB with chemotherapeutic agents, deeper and more sustained anti-tumor responses were observed when compared to monotherapy. Together with the potential to deliver a favorable safety profile, these data support clinical testing of TR2/CDH3 BAB in patients with PDAC.

Dual targeting of DR5 and VEGFR2 molecular pathways by multivalent fusion protein significantly suppresses tumor growth and angiogenesis

Destroying tumor vasculature is a relevant therapeutic strategy due to its involvement in tumor progression. However, adaptive resistance to approved antiangiogenic drugs targeting VEGF/VEGFR pathway requires the recruitment of additional targets. In this aspect, targeting TRAIL pathway is promising as it is an important component of the immune system involved in tumor immunosurveillance. For dual targeting of malignant cells and tumor vascular microenvironment, we designed a multivalent fusion protein SRH-DR5-B-iRGD with antiangiogenic VEGFR2-specific peptide SRH at the N-terminus and a tumor-targeting and -penetrating peptide iRGD at the C-terminus of receptor-selective TRAIL variant DR5-B. SRH-DR5-B-iRGD obtained high affinity for DR5, VEGFR2 and αvβ3 integrin in nanomolar range. Fusion of DR5-B with effector peptides accelerated DR5 receptor internalization rate upon ligand binding. Antitumor efficacy was evaluated in vitro in human tumor cell lines and primary patient-derived glioblastoma neurospheres, and in vivo in xenograft mouse model of human glioblastoma. Multivalent binding of SRH-DR5-B-iRGD fusion efficiently stimulated DR5-mediated tumor cell death via caspase-dependent mechanism, suppressed xenograft tumor growth by >80 %, doubled the lifespan of xenograft animals, and inhibited tumor vascularization. Therefore, targeting DR5 and VEGFR2 molecular pathways with SRH-DR5-B-iRGD protein may provide a novel therapeutic approach for treatment of solid tumors.

Aponermin or placebo in combination with thalidomide and dexamethasone in the treatment of relapsed or refractory multiple myeloma (CPT-MM301): a randomised, double-blinded, placebo-controlled, phase 3 trial

BACKGROUND

Aponermin, a circularly permuted tumor necrosis factor-related apoptosis-inducing ligand, is a potential death receptor 4/5-targeted antitumour candidate. Previous phase 1/2 studies have demonstrated the efficacy of aponermin in patients with relapsed or refractory multiple myeloma (RRMM). To confirm the superiority of aponermin plus thalidomide and dexamethasone (aponermin group) over placebo plus thalidomide and dexamethasone (placebo group) in RRMM, a randomized, double-blinded, placebo controlled phase 3 trial was performed.

METHODS

Four hundred seventeen patients with RRMM who had previously received at least two regimens were randomly assigned (2:1) to receive aponermin, thalidomide, and dexamethasone or placebo, thalidomide, and dexamethasone. The primary endpoint was progression-free survival (PFS). Key secondary endpoints included overall survival (OS) and overall response rate (ORR).

RESULTS

A total of 415 patients received at least one dose of trial treatment (276 vs. 139). The median PFS was 5.5 months in the aponermin group and 3.1 months in the placebo group (hazard ratio, 0.62; 95% confidence interval [CI], 0.49-0.78; P < 0.001). The median OS was 22.4 months for the aponermin group and 16.4 months for the placebo group (hazard ratio, 0.70; 95% CI, 0.55-0.89; P = 0.003). Significantly higher rates of ORR (30.4% vs. 13.7%, P < 0.001) and very good partial response or better (14.1% vs. 2.2%, P < 0.0001) were achieved in the aponermin group than in the placebo group. Treatment with aponermin caused hepatotoxicity in some patients, as indicated by the elevated alanine transaminase, aspartate transaminase, or lactate dehydrogenase levels (52.2% vs. 24.5%, 51.1% vs. 19.4% and 44.9% vs. 21.6%, respectively), mostly grade 1/2, transient and reversible. The main grade 3/4 adverse events included neutropenia, pneumonia and hyperglycemia. The incidence of serious adverse events was similar between the two groups (40.6% vs. 37.4%). There was no evidence that aponermin leads to hematological toxicity, nephrotoxicity, cardiotoxicity, or secondary tumors.

CONCLUSIONS

Aponermin plus thalidomide and dexamethasone significantly improved PFS, OS and ORR with manageable side effects in RRMM patients who had received at least two prior therapies. These results support the use of aponermin, thalidomide, and dexamethasone as a treatment option for RRMM patients.

TRIAL REGISTRATION

The trial was registered at http://www.chictr.org.cn as ChiCTR-IPR-15006024, 17/11/2014.

Snoopligase-catalyzed molecular glue enables efficient generation of hyperoligomerized TRAIL variant with enhanced antitumor effect

Clinical application of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is predominantly limited by its inefficient apoptosis induction in tumor cells, which might be improved by using molecular superglue-mediated hyperoligomerization to increase its valency. Here, the minimal superglue peptide pairs, including Snoopligase-catalyzed SnoopTagJr/SnoopDogTag and SpyStapler-catalyzed SpyTag/SpyBDTag, were individually fused at the N- or C-terminus of the TRAIL promoter to produce superglue-fusion TRAIL variants. Similar to native trivalent TRAIL, these superglue-fusion TRAIL variants were highly expressed in Escherichia coli (E. coli) and spontaneously trimerized. In the presence of Snoopligase or SpyStapler, the trivalent superglue-fusion TRAIL variants were predominantly crosslinked into hexavalent TRAIL variants. Nevertheless, Snoopligase was more efficient than SpyStapler in the production of hexavalent TRAIL variants. In particular, Snoopligase-catalyzed trivalent TRAIL variants with N-terminal fusion of SnoopTagJr/SnoopDogTag produced hexavalent SnHexaTR with the highest yield (∼70%). The in vitro cytotoxicity of SnHexaTR was 10-40 times greater than that of TRAIL in several tumor cells. In addition, compared to trivalent TRAIL, hexavalent SnHexaTR showed a longer serum half-life and greater tumor uptake, which resulted in eradication of 50% of tumor xenografts of TRAIL-sensitive COLO 205. In mice bearing TRAIL-resistant HT-29 tumor xenografts, hexavalent SnHexaTR combined with bortezomib encapsulated in liposomes also showed robust tumor growth suppression, indicating that hyperoligomerization mediated by minimal molecular superglue significantly increased the cytotoxicity and antitumor effect of TRAIL. As a novel anticancer agent candidate, the hexavalent SnHexaTR has great potential for clinical application in cancer therapy.

Sex Differences in Lung Cancer

Sex disparities in the incidence and mortality of lung cancer have been observed since cancer statistics have been recorded. Social and economic differences contribute to sex disparities in lung cancer incidence and mortality, but evidence suggests that there are also underlying biological differences that contribute to the disparity. This review summarizes biological differences which could contribute to the sex disparity. Sex hormones and other biologically active molecules, tumor cell genetic differences, and differences in the immune system and its response to lung cancer are highlighted. How some of these differences contribute to disparities in the response to therapies, including cytotoxic, targeted, and immuno-therapies, is also discussed. We end the study with a discussion of our perceived future directions to identify the key biological differences which could contribute to sex disparities in lung cancer and how these differences could be therapeutically leveraged to personalize lung cancer treatment to the individual sexes.

Molecular superglue-mediated higher-order assembly of TRAIL variants with superior apoptosis induction and antitumor activity

Prompting higher-order death receptor (DR) clustering by increasing the valency of DR agonist is efficient to induce apoptosis of tumor cells. As an attractive DR agonist with superior biosafety, the trimeric tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) exerts limited antitumor effect in patients, which is predominantly attributed to its low DR clustering ability and short serum half-life. Previous antibody scaffolds-based engineering strategies to increase the valency and/or prolong the serum half-life of TRAIL improve apoptosis induction, however, often produce large proteins with poor tumor penetration. Covalent protein ligation mediated by small molecular superglues such as SpyTag/SpyCatcher might be a novel strategy to assemble higher-order TRAIL variants. Upon fusion to TRAIL promotor, SpyTag/SpyCatcher molecular superglue preferentially ligated two trimeric TRAIL to produce a hexameric TRAIL variant, HexaTR, exhibiting a significantly increased apoptosis induction. In addition, an albumin-binding HexaTR, ABD-HexaTR, with a prolonged serum half-life by binding to endogenous albumin was also produced using the same strategy. Compared to the trimeric TRAIL, the hexameric HexaTR and ABD-HexaTR showed 20-50 times greater in vivo antitumor effect, resulting in eradication of several types of large (150-300 mm³) tumor xenografts. Combination with bortezomib carried by liposome further improved the antitumor effects of the hexavalent HexaTR and ABD-HexaTR in refractory cancer. Our results indicate that the superglue-mediated higher-order assembly is promising to improve the DR clustering and proapoptotic signaling of TRAIL, showing great advantages in constructing the next generation of DR agonists for cancer therapy.

Targeting regulated cell death pathways in acute myeloid leukemia

The use of the BCL2 inhibitor venetoclax has transformed the management of patients with acute myeloid leukemia (AML) who are ineligible for intensive chemotherapy. By triggering intrinsic apoptosis, the drug is an excellent illustration of how our greater understanding of molecular cell death pathways can be translated into the clinic. Nevertheless, most venetoclax-treated patients will relapse, suggesting the need to target additional regulated cell death pathways. To highlight advances in this strategy, we review the recognized regulated cell death pathways, including apoptosis, necroptosis, ferroptosis and autophagy. Next, we detail the therapeutic opportunities to trigger regulated cell death in AML. Finally, we describe the main drug discovery challenges for regulated cell death inducers and their translation into clinical trials. A better knowledge of the molecular pathways regulating cell death represents a promising strategy to develop new drugs to cure resistant or refractory AML patients, particularly those resistant to intrinsic apoptosis.

Therapeutic targeting of TRAIL death receptors

The discovery of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) along with its potent and selective antitumor effects initiated a decades-long search for therapeutic strategies to target the TRAIL pathway. First-generation approaches were focused on the development of TRAIL receptor agonists (TRAs), including recombinant human TRAIL (rhTRAIL) and TRAIL receptor-targeted agonistic antibodies. While such TRAIL pathway-targeted therapies showed promise in preclinical data and clinical trials have been conducted, none have advanced to FDA approval. Subsequent second-generation approaches focused on improving upon the specific limitations of first-generation approaches by ameliorating the pharmacokinetic profiles and agonistic abilities of TRAs as well as through combinatorial approaches to circumvent resistance. In this review, we summarize the successes and shortcomings of first- and second-generation TRAIL pathway-based therapies, concluding with an overview of the discovery and clinical introduction of ONC201, a compound with a unique mechanism of action that represents a new generation of TRAIL pathway-based approaches. We discuss preclinical and clinical findings in different tumor types and provide a unique perspective on translational directions of the field.

Harnessing TRAIL-induced cell death for cancer therapy: a long walk with thrilling discoveries

Tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) can induce apoptosis in a wide variety of cancer cells, both in vitro and in vivo, importantly without killing any essential normal cells. These findings formed the basis for the development of TRAIL-receptor agonists (TRAs) for cancer therapy. However, clinical trials conducted with different types of TRAs have, thus far, afforded only limited therapeutic benefit, as either the respectively chosen agonist showed insufficient anticancer activity or signs of toxicity, or the right TRAIL-comprising combination therapy was not employed. Therefore, in this review we will discuss molecular determinants of TRAIL resistance, the most promising TRAIL-sensitizing agents discovered to date and, importantly, whether any of these could also prove therapeutically efficacious upon cancer relapse following conventional first-line therapies. We will also discuss the more recent progress made with regards to the clinical development of highly active non-immunogenic next generation TRAs. Based thereupon, we next propose how TRAIL resistance might be successfully overcome, leading to the possible future development of highly potent, cancer-selective combination therapies that are based on our current understanding of biology TRAIL-induced cell death. It is possible that such therapies may offer the opportunity to tackle one of the major current obstacles to effective cancer therapy, namely overcoming chemo- and/or targeted-therapy resistance. Even if this were achievable only for certain types of therapy resistance and only for particular types of cancer, this would be a significant and meaningful achievement.

Small-molecule inhibitors, immune checkpoint inhibitors, and more: FDA-approved novel therapeutic drugs for solid tumors from 1991 to 2021

The United States Food and Drug Administration (US FDA) has always been a forerunner in drug evaluation and supervision. Over the past 31 years, 1050 drugs (excluding vaccines, cell-based therapies, and gene therapy products) have been approved as new molecular entities (NMEs) or biologics license applications (BLAs). A total of 228 of these 1050 drugs were identified as cancer therapeutics or cancer-related drugs, and 120 of them were classified as therapeutic drugs for solid tumors according to their initial indications. These drugs have evolved from small molecules with broad-spectrum antitumor properties in the early stage to monoclonal antibodies (mAbs) and antibody‒drug conjugates (ADCs) with a more precise targeting effect during the most recent decade. These drugs have extended indications for other malignancies, constituting a cancer treatment system for monotherapy or combined therapy. However, the available targets are still mainly limited to receptor tyrosine kinases (RTKs), restricting the development of antitumor drugs. In this review, these 120 drugs are summarized and classified according to the initial indications, characteristics, or functions. Additionally, RTK-targeted therapies and immune checkpoint-based immunotherapies are also discussed. Our analysis of existing challenges and potential opportunities in drug development may advance solid tumor treatment in the future.

Pharmacologic Targeting of TFIIH Suppresses KRAS-Mutant Pancreatic Ductal Adenocarcinoma and Synergizes with TRAIL

Pancreatic ductal adenocarcinoma (PDAC) typically presents as metastatic disease at diagnosis and remains refractory to treatment. Next-generation sequencing efforts have described the genomic landscape, classified molecular subtypes, and confirmed frequent alterations in major driver genes, with coexistent alterations in KRAS and TP53 correlating with the highest metastatic burden and poorest outcomes. However, translating this information to guide therapy remains a challenge. By integrating genomic analysis with an arrayed RNAi druggable genome screen and drug profiling of a KRAS/TP53 mutant PDAC cell line derived from a patient-derived xenograft (PDCL), we identified numerous targetable vulnerabilities that reveal both known and novel functional aspects of pancreatic cancer biology. A dependence on the general transcription and DNA repair factor TFIIH complex, particularly the XPB subunit and the CAK complex (CDK7/CyclinH/MAT1), was identified and further validated utilizing a panel of genomically subtyped KRAS mutant PDCLs. TFIIH function was inhibited with a covalent inhibitor of CDK7/12/13 (THZ1), a CDK7/CDK9 kinase inhibitor (SNS-032), and a covalent inhibitor of XPB (triptolide), which led to disruption of the protein stability of the RNA polymerase II subunit RPB1. Loss of RPB1 following TFIIH inhibition led to downregulation of key transcriptional effectors of KRAS-mutant signaling and negative regulators of apoptosis, including MCL1, XIAP, and CFLAR, initiating caspase-8 dependent apoptosis. All three drugs exhibited synergy in combination with a multivalent TRAIL, effectively reinforcing mitochondrial-mediated apoptosis. These findings present a novel combination therapy, with direct translational implications for current clinical trials on metastatic pancreatic cancer patients. Significance: This study utilizes functional genetic and pharmacological profiling of KRAS-mutant pancreatic adenocarcinoma to identify therapeutic strategies and finds that TFIIH inhibition synergizes with TRAIL to induce apoptosis in KRAS-driven pancreatic cancer.

Regulated cell death (RCD) in cancer: key pathways and targeted therapies

Regulated cell death (RCD), also well-known as programmed cell death (PCD), refers to the form of cell death that can be regulated by a variety of biomacromolecules, which is distinctive from accidental cell death (ACD). Accumulating evidence has revealed that RCD subroutines are the key features of tumorigenesis, which may ultimately lead to the establishment of different potential therapeutic strategies. Hitherto, targeting the subroutines of RCD with pharmacological small-molecule compounds has been emerging as a promising therapeutic avenue, which has rapidly progressed in many types of human cancers. Thus, in this review, we focus on summarizing not only the key apoptotic and autophagy-dependent cell death signaling pathways, but the crucial pathways of other RCD subroutines, including necroptosis, pyroptosis, ferroptosis, parthanatos, entosis, NETosis and lysosome-dependent cell death (LCD) in cancer. Moreover, we further discuss the current situation of several small-molecule compounds targeting the different RCD subroutines to improve cancer treatment, such as single-target, dual or multiple-target small-molecule compounds, drug combinations, and some new emerging therapeutic strategies that would together shed new light on future directions to attack cancer cell vulnerabilities with small-molecule drugs targeting RCD for therapeutic purposes.

Eftozanermin alfa (ABBV-621) monotherapy in patients with previously treated solid tumors: findings of a phase 1, first-in-human study

Eftozanermin alfa (eftoza), a second-generation tumor necrosis factor-related apoptosis-inducing ligand receptor (TRAIL-R) agonist, induces apoptosis in tumor cells by activation of death receptors 4/5. This phase 1 dose-escalation/dose-optimization study evaluated the safety, pharmacokinetics, pharmacodynamics, and preliminary activity of eftoza in patients with advanced solid tumors. Patients received eftoza 2.5-15 mg/kg intravenously on day 1 or day 1/day 8 every 21 days in the dose-escalation phase, and 1.25-7.5 mg/kg once-weekly (QW) in the dose-optimization phase. Dose-limiting toxicities (DLTs) were evaluated during the first treatment cycle to determine the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D). Pharmacodynamic effects were evaluated in circulation and tumor tissue. A total of 105 patients were enrolled in the study (dose-escalation cohort, n = 57; dose-optimization cohort, n = 48 patients [n = 24, colorectal cancer (CRC); n = 24, pancreatic cancer (PaCA)]). In the dose-escalation cohort, seven patients experienced DLTs. MTD and RP2D were not determined. Most common treatment-related adverse events were increased alanine aminotransferase and aspartate aminotransferase levels, nausea, and fatigue. The one treatment-related death occurred due to respiratory failure. In the dose-optimization cohort, three patients (CRC, n = 2; PaCA, n = 1) had a partial response. Target engagement with regard to receptor saturation, and downstream apoptotic pathway activation in circulation and tumor were observed. Eftoza had acceptable safety, evidence of pharmacodynamic effects, and preliminary anticancer activity. The 7.5-mg/kg QW regimen was selected for future studies on the basis of safety findings, pharmacodynamic effects, and biomarker modulations. (Trial registration number: NCT03082209 (registered: March 17, 2017)).

Optimized Heterologous Expression and Efficient Purification of a New TRAIL-Based Antitumor Fusion Protein SRH-DR5-B with Dual VEGFR2 and DR5 Receptor Specificity

In the last two decades, bifunctional proteins have been created by genetic and protein engineering methods to increase therapeutic effects in various diseases, including cancer. Unlike conventional small molecule or monotargeted drugs, bifunctional proteins have increased biological activity while maintaining low systemic toxicity. The recombinant anti-cancer cytokine TRAIL has shown a limited therapeutic effect in clinical trials. To enhance the efficacy of TRAIL, we designed the HRH–DR5-B fusion protein based on the DR5-selective mutant variant of TRAIL fused to the anti-angiogenic synthetic peptide HRHTKQRHTALH. Initially low expression of HRH–DR5-B was enhanced by the substitution of E. coli-optimized codons with AT-rich codons in the DNA sequence encoding the first 7 amino acid residues of the HRH peptide. However, the HRH–DR5-B degraded during purification to form two adjacent protein bands on the SDS-PAGE gel. The replacement of His by Ser at position P2 immediately after the initiator Met dramatically minimized degradation, allowing more than 20 mg of protein to be obtained from 200 mL of cell culture. The resulting SRH–DR5-B fusion bound the VEGFR2 and DR5 receptors with high affinity and showed increased cytotoxic activity in 3D multicellular tumor spheroids. SRH–DR5-B can be considered as a promising candidate for therapeutic applications.

Cell cycle progression and transmitotic apoptosis resistance promote escape from extrinsic apoptosis

Extrinsic apoptosis relies on TNF-family receptor activation by immune cells or receptor-activating drugs. Here, we monitored cell cycle progression at a resolution of minutes to relate apoptosis kinetics and cell-to-cell heterogeneities in death decisions to cell cycle phases. Interestingly, we found that cells in S phase delay TRAIL receptor-induced death in favour of mitosis, thereby passing on an apoptosis-primed state to their offspring. This translates into two distinct fates, apoptosis execution post mitosis or cell survival from inefficient apoptosis. Transmitotic resistance is linked to Mcl-1 upregulation and its increased accumulation at mitochondria from mid-S phase onwards, which allows cells to pass through mitosis with activated caspase-8, and with cells escaping apoptosis after mitosis sustaining sublethal DNA damage. Antagonizing Mcl-1 suppresses cell cycle-dependent delays in apoptosis, prevents apoptosis-resistant progression through mitosis and averts unwanted survival after apoptosis induction. Cell cycle progression therefore modulates signal transduction during extrinsic apoptosis, with Mcl-1 governing decision making between death, proliferation and survival. Cell cycle progression thus is a crucial process from which cell-to-cell heterogeneities in fates and treatment outcomes emerge in isogenic cell populations during extrinsic apoptosis. This article has an associated First Person interview with the first author of the paper.

Low-Level Endothelial TRAIL-Receptor Expression Obstructs the CNS-Delivery of Angiopep-2 Functionalised TRAIL-Receptor Agonists for the Treatment of Glioblastoma

Glioblastoma (GBM) is the most malignant and aggressive form of glioma and is associated with a poor survival rate. Latest generation Tumour Necrosis Factor Related Apoptosis-Inducing Ligand (TRAIL)-based therapeutics potently induce apoptosis in cancer cells, including GBM cells, by binding to death receptors. However, the blood-brain barrier (BBB) is a major obstacle for these biologics to enter the central nervous system (CNS). We therefore investigated if antibody-based fusion proteins that combine hexavalent TRAIL and angiopep-2 (ANG2) moieties can be developed, with ANG2 promoting receptor-mediated transcytosis (RMT) across the BBB. We demonstrate that these fusion proteins retain the potent apoptosis induction of hexavalent TRAIL-receptor agonists. Importantly, blood-brain barrier cells instead remained highly resistant to this fusion protein. Binding studies indicated that ANG2 is active in these constructs but that TRAIL-ANG2 fusion proteins bind preferentially to BBB endothelial cells via the TRAIL moiety. Consequently, transport studies indicated that TRAIL-ANG2 fusion proteins can, in principle, be shuttled across BBB endothelial cells, but that low TRAIL receptor expression on BBB endothelial cells interferes with efficient transport. Our work therefore demonstrates that TRAIL-ANG2 fusion proteins remain highly potent in inducing apoptosis, but that therapeutic avenues will require combinatorial strategies, such as TRAIL-R masking, to achieve effective CNS transport.

Multimeric Anti-DR5 IgM Agonist Antibody IGM-8444 Is a Potent Inducer of Cancer Cell Apoptosis and Synergizes with Chemotherapy and BCL-2 Inhibitor ABT-199

Death receptor 5 (DR5) is an attractive target for cancer therapy due to its broad upregulated expression in multiple cancers and ability to directly induce apoptosis. Though anti-DR5 IgG antibodies have been evaluated in clinical trials, limited efficacy has been attributed to insufficient receptor crosslinking. IGM-8444 is an engineered, multivalent agonistic IgM antibody with 10 binding sites to DR5 that induces cancer cell apoptosis through efficient DR5 multimerization. IGM-8444 bound to DR5 with high avidity and was substantially more potent than an IgG with the same binding domains. IGM-8444 induced cytotoxicity in a broad panel of solid and hematologic cancer cell lines but did not kill primary human hepatocytes in vitro, a potential toxicity of DR5 agonists. In multiple xenograft tumor models, IGM-8444 monotherapy inhibited tumor growth, with strong and sustained tumor regression observed in a gastric PDX model. When combined with chemotherapy or the BCL-2 inhibitor ABT-199, IGM-8444 exhibited synergistic in vitro tumor cytotoxicity and enhanced in vivo efficacy, without augmenting in vitro hepatotoxicity. These results support the clinical development of IGM-8444 in solid and hematologic malignancies as a monotherapy and in combination with chemotherapy or BCL-2 inhibition.

Mesenchymal type neuroblastoma cells escape ALK inhibitors

Cancer therapy frequently fails due to the emergence of resistance. Many tumors include phenotypically immature tumor cells, which have been implicated in therapy resistance. Neuroblastoma cells can adopt a lineage committed adrenergic (ADRN) or an immature mesenchymal (MES) state. They differ in epigenetic landscape and transcription factors, and MES cells are more resistant to chemotherapy. Here we analyzed the response of MES cells to targeted drugs. Activating ALK mutations are frequently found in neuroblastoma and ALK inhibitors (ALKi) are in clinical trials. ALKi treatment of ADRN neuroblastoma cells with a tumor-driving ALK mutation induced cell death. Conversely, MES cells did not express either mutant or wild-type ALK and were resistant to ALKi, and MES cells formed tumors that progressed under ALKi therapy. In assessing the role of MES cells in relapse development, TRAIL was identified to specifically induce apoptosis in MES cells and suppress MES tumor growth. Addition of TRAIL to ALKi treatment of neuroblastoma xenografts delayed relapses in a subset of the animals, suggesting a role for MES cells in relapse formation. While ADRN cells resembled normal embryonal neuroblasts, MES cells resembled immature precursor cells which also lacked ALK expression. Resistance to targeted drugs can therefore be an intrinsic property of immature cancer cells based on their resemblance to developmental precursors.

BH3-only protein expression determines hepatocellular carcinoma response to sorafenib-based treatment

Hepatocellular carcinoma (HCC) represents a global health challenge with limited therapeutic options. Anti-angiogenic immune checkpoint inhibitor-based combination therapy has been introduced for progressed HCC, but improves survival only in a subset of HCC patients. Tyrosine-kinase inhibitors (TKI) such as sorafenib represent an alternative treatment option but have only modest efficacy. Using different HCC cell lines and HCC tissues from various patients reflecting HCC heterogeneity, we investigated whether the sorafenib response could be enhanced by combination with pro-apoptotic agents, such as TNF-related apoptosis-inducing ligand (TRAIL) or the BH3-mimetic ABT-737, which target the death receptor and mitochondrial pathway of apoptosis, respectively. We found that both agents could enhance sorafenib-induced cell death which was, however, dependent on specific BH3-only proteins. TRAIL augmented sorafenib-induced cell death only in NOXA-expressing HCC cells, whereas ABT-737 enhanced the sorafenib response also in NOXA-deficient cells. ABT-737, however, failed to augment sorafenib cytotoxicity in the absence of BIM, even when NOXA was strongly expressed. In the presence of NOXA, BIM-deficient HCC cells could be in turn strongly sensitized for cell death induction by the combination of sorafenib with TRAIL. Accordingly, HCC tissues sensitive to apoptosis induction by sorafenib and TRAIL revealed enhanced NOXA expression compared to HCC tissues resistant to this treatment combination. Thus, our results suggest that BH3-only protein expression determines the treatment response of HCC to different sorafenib-based drug combinations. Individual profiling of BH3-only protein expression might therefore assist patient stratification to certain TKI-based HCC therapies.