A novel anti-HER2 anthracycline-based antibody-drug conjugate induces adaptive anti-tumor immunity and potentiates PD-1 blockade in breast cancer

Recent advances in sialic acid-based active targeting chemoimmunotherapy promoting tumor shedding: a systematic review

Tumors have always been a major public health concern worldwide, and attempts to look for effective treatments have never ceased. Sialic acid is known to be a crucial element for tumor development and its receptors are highly expressed on tumor-associated immune cells, which perform significant roles in establishing the immunosuppressive tumor microenvironment and further boosting tumorigenesis, progression, and metastasis. Obviously, it is essential to consider sophisticated crosstalk between tumors, the immune system, and preparations, and understand the links between pharmaceutics and immunology. Sialic acid-based chemoimmunotherapy enables active targeting drug delivery via mediating the recognition between the sialic acid-modified nano-drug delivery system represented by liposomes and sialic acid-binding receptors on tumor-associated immune cells, which inhibit their activity and utilize their homing ability to deliver drugs. Such a "Trojan horse" strategy has remarkably improved the shortcomings of traditional passive targeting treatments, unexpectedly promoted tumor shedding, and persistently induced robust immunological memory, thus highlighting its prospective application potential for targeting various tumors. Herein, we review recent advances in sialic acid-based active targeting chemoimmunotherapy to promote tumor shedding, summarize the current viewpoints on the tumor shedding mechanism, especially the formation of durable immunological memory, and analyze the challenges and opportunities of this attractive approach.

Trop-2 expression and the tumor immune microenvironment in cervical cancer

OBJECTIVE

Trophoblast Cell Surface Antigen 2 (Trop-2) is a transmembrane glycoprotein that is overexpressed in various cancers, with immunological significance as a target for tumor-reactive T-cells. We aimed to investigate the association between the expression of Trop-2 and the tumor immune microenvironment in cervical cancer.

METHODS

The study included 123 patients with cervical cancer who underwent primary surgery between 2000 and 2020 in our hospital. Trop-2 expression was evaluated using anti-Trop-2 monoclonal antibody clone MAB650. Immune biomarkers, including PD-L1 (22C3), CD3 (PS1), and CD8 (4B11), were also evaluated. Trop-2 and PD-L1 positivity were defined by an H-score ≥ 10 and a combined positive score (CPS) ≥1, respectively. Tumor-infiltrating lymphocytes (TILs) were assessed in the five selected independent areas. The correlation between Trop-2 expression and immune biomarkers was analyzed.

RESULTS

The cohort comprised patients with squamous cell carcinoma (SCC) (54.5%) and non-SCC (45.5%). Trop-2 was positive in 84.6% of samples and more commonly expressed in SCC (SCC vs. non-SCC; 97.0% vs. 69.6%, p < 0.001). Intratumoral CD3+ and CD8 + TILs were significantly more common in Trop-2-positive cases (CD3, Mann-Whitney U = 383, p < 0.0001; CD8, U = 442, p < 0.0001). Additionally, significant positive correlations were found between the Trop-2 H-score and immune markers (CD3 + TILs, r = 0.295, p < 0.001; CD8 + TILs, r = 0.267, p = 0.001; PD-L1 CPS, r = 0.178, p = 0.025). No significant associations were detected between TILs and other clinicopathological features, including prognosis.

CONCLUSION

Expression of Trop-2 in cervical cancer is associated with increased levels of intratumoral TILs, indicating the potential of Trop-2 targeted therapy alone or in combination with immune checkpoint inhibitors.

Antibody-Drug Conjugates to Promote Immune Surveillance: Lessons Learned from Breast Cancer

Antibody-drug conjugates (ADCs) represent an effective class of agents for the treatment of several tumor types, including breast cancer (BC), featuring approved molecules such as trastuzumab-emtansine, trastuzumab-deruxtecan, and sacituzumab-govitecan. Immune-checkpoint inhibitors (ICIs) also showed activity in selected BC subtypes, and two agents, pembrolizumab and atezolizumab, are currently approved for the treatment of triple-negative BC patients. The potential synergy between ADCs and immunotherapy in BC remains an area of active investigation. Preclinical studies suggest that ADCs promote immune surveillance, modulating tumor microenvironment, inducing immunogenic cell death, and enhancing antitumor immunity. Translational evidence has shown potential predictive biomarkers for ADCs alone or in combination with immunotherapy, including expression of target antigen, oncogenic pathways, tumor-infiltrating lymphocytes, and neutrophil-to-lymphocyte ratio. Given this background, several clinical trials evaluated ADC-ICI combinations in BC patients, demonstrating promising outcomes with an overall manageable toxicity profile, and many studies are currently ongoing to confirm the efficacy and feasibility of this therapeutic approach. In the present review, we summarized the available evidence about the integration of ADCs and immunotherapy for the management of BC, emphasizing the need for further translational and clinical investigations to optimize this treatment strategy and elucidate predictive biomarkers, eventually improving patient outcomes.

Mechanistic Characterization of Cancer-associated Fibroblast Depletion via an Antibody-Drug Conjugate Targeting Fibroblast Activation Protein

Cancer-associated fibroblasts (CAF) are a prominent cell type within the tumor microenvironment (TME) where they are known to promote cancer cell growth and survival, angiogenesis, drug resistance, and immunosuppression. The transmembrane prolyl protease fibroblast activation protein (FAP) is expressed on the surface of highly protumorigenic CAFs found in the stroma of nearly every cancer of epithelial origin. The widespread expression of FAP has made it an attractive therapeutic target based on the underlying hypothesis that eliminating protumorigenic CAFs will disrupt the cross-talk between components of TME resulting in cancer cell death and immune infiltration. This hypothesis, however, has never been directly proven. To eliminate FAP-expressing CAFs, we developed an antibody-drug conjugate using our anti-FAP antibody, huB12, coupled to a monomethyl auristatin E (huB12-MMAE) payload. After determining that huB12 was an effective targeting vector, we found that huB12-MMAE potently eliminated FAP-expressing cells as monocultures in vitro and significantly prolonged survival in vivo using a xenograft engineered to overexpress FAP. We investigated the effects of selectively eliminating CAFs using a layered, open microfluidic cell coculture platform, known as the Stacks. Analysis of mRNA and protein expression found that treatment with huB12-MMAE resulted in the increased secretion of the proinflammatory cytokines IL6 and IL8 by CAFs and an associated increase in expression of proinflammatory genes in cancer cells. We also detected increased secretion of CSF1, a cytokine involved in myeloid recruitment and differentiation. Our findings suggest that the mechanism of FAP-targeted therapies is through effects on the immune microenvironment and antitumor immune response.

SIGNIFICANCE

The direct elimination of FAP-expressing CAFs disrupts the cross-talk with cancer cells leading to a proinflammatory response and alterations in the immune microenvironment and antitumor immune response.

Clinical translation of antibody drug conjugate dosing in solid tumors from preclinical mouse data

Antibody drug conjugates (ADCs) have made impressive strides in the clinic in recent years with 11 Food and Drug Administration approvals, including 6 for the treatment of patients with solid tumors. Despite this success, the development of new agents remains challenging with a high failure rate in the clinic. Here, we show that current approved ADCs for the treatment of patients with solid tumors can all show substantial efficacy in some mouse models when administered at a similar weight-based [milligrams per kilogram (mg/kg)] dosing in mice that is tolerated in the clinic. Mechanistically, equivalent mg/kg dosing results in a similar drug concentration in the tumor and a similar tissue penetration into the tumor due to the unique delivery features of ADCs. Combined with computational approaches, which can account for the complex distribution within the tumor microenvironment, these scaling concepts may aid in the evaluation of new agents and help design therapeutics with maximum clinical efficacy.

HER2-Altered Non-Small Cell Lung Cancer: A Journey from Current Approaches to Emerging Strategies

For patients diagnosed with advanced HER2-altered non-small cell lung cancer (NSCLC), the current standard of care is represented by a platinum-pemetrexed-based chemotherapy, eventually in combination with immunotherapy. Different pan-HER tyrosine kinase inhibitors have been evaluated in limited phase II trials, yielding generally unsatisfactory outcomes, although certain genotypes demonstrated some clinical benefit. Conversely, antibody-drug conjugates (ADCs) targeting HER2, particularly trastuzumab-deruxtecan, have shown promising results against HER2-mutant disease, including a great intracranial activity in patients with brain metastasis. Based on the results obtained from DESTINY-Lung01 and DESTINY-Lung02 trials, trastuzumab deruxtecan received regulatory approval as the first targeted therapy for pre-treated, HER2-mutant, advanced NSCLC patients. More recently, the Food and Drug Administration (FDA) granted the accelerated approval of trastuzumab deruxtecan for advanced, pre-treated HER2-positive solid tumours with no other treatment options. In this scenario, emerging evidence is increasingly pointing towards the exploration of combination regimens with synergistic effects in the advanced disease. In this review, we provide a detailed summary of current approaches and emerging strategies in the management of HER2-altered NSCLC, also focusing on unmet needs, including the treatment of patients with brain metastases.

Targeting TACC3 Induces Immunogenic Cell Death and Enhances T-DM1 Response in HER2-Positive Breast Cancer

Trastuzumab emtansine (T-DM1) was the first and one of the most successful antibody-drug conjugates (ADC) approved for treating refractory HER2-positive breast cancer. Despite its initial clinical efficacy, resistance is unfortunately common, necessitating approaches to improve response. Here, we found that in sensitive cells, T-DM1 induced spindle assembly checkpoint (SAC)-dependent immunogenic cell death (ICD), an immune-priming form of cell death. The payload of T-DM1 mediated ICD by inducing eIF2α phosphorylation, surface exposure of calreticulin, ATP and HMGB1 release, and secretion of ICD-related cytokines, all of which were lost in resistance. Accordingly, ICD-related gene signatures in pretreatment samples correlated with clinical response to T-DM1-containing therapy, and increased infiltration of antitumor CD8+ T cells in posttreatment samples was correlated with better T-DM1 response. Transforming acidic coiled-coil containing 3 (TACC3) was overexpressed in T-DM1-resistant cells, and T-DM1 responsive patients had reduced TACC3 protein expression whereas nonresponders exhibited increased TACC3 expression during T-DM1 treatment. Notably, genetic or pharmacologic inhibition of TACC3 restored T-DM1-induced SAC activation and induction of ICD markers in vitro. Finally, TACC3 inhibition in vivo elicited ICD in a vaccination assay and potentiated the antitumor efficacy of T-DM1 by inducing dendritic cell maturation and enhancing intratumoral infiltration of cytotoxic T cells. Together, these results illustrate that ICD is a key mechanism of action of T-DM1 that is lost in resistance and that targeting TACC3 can restore T-DM1-mediated ICD and overcome resistance.

SIGNIFICANCE

Loss of induction of immunogenic cell death in response to T-DM1 leads to resistance that can be overcome by targeting TACC3, providing an attractive strategy to improve the efficacy of T-DM1.

Amine-Carbamate Self-Immolative Spacers Counterintuitively Release 3° Alcohol at Much Faster Rates than 1° Alcohol Payloads

Self-immolative (SI) spacers are degradable chemical connectors widely used in prodrugs and drug conjugates to release pharmaceutical ingredients in response to specific stimuli. Amine-carbamate SI spacers are particularly versatile, as they have been used to release different hydroxy cargos, ranging from 2° and 3° alcohols to phenols and oximes. In this work, we describe the ability of three amine-carbamate SI spacers to release three structurally similar imidazoquinoline payloads, bearing either a 1°, a 2° or a 3° alcohol as the leaving group. While the spacers showed comparable efficacy at releasing the 2° and 3° alcohols, the liberation of the 1° alcohol was much slower, unveiling a counterintuitive trend in nucleophilic acyl substitutions. The release of the 1° alcohol payload was only possible using a SI spacer bearing a pyrrolidine ring and a tertiary amine handle, which opens the way to future applications in drug delivery systems.

Cancer immunometabolism: advent, challenges, and perspective

For decades, great strides have been made in the field of immunometabolism. A plethora of evidence ranging from basic mechanisms to clinical transformation has gradually embarked on immunometabolism to the center stage of innate and adaptive immunomodulation. Given this, we focus on changes in immunometabolism, a converging series of biochemical events that alters immune cell function, propose the immune roles played by diversified metabolic derivatives and enzymes, emphasize the key metabolism-related checkpoints in distinct immune cell types, and discuss the ongoing and upcoming realities of clinical treatment. It is expected that future research will reduce the current limitations of immunotherapy and provide a positive hand in immune responses to exert a broader therapeutic role.

Targeting MET in NSCLC: An Ever-Expanding Territory

MET protooncogene (MET) alterations are known driver oncogenes in NSCLC. Since the identification of MET as a potential therapeutic target, extensive clinical trials have been performed. As a result, MET-targeted therapies, including MET tyrosine kinase inhibitors, monoclonal antibodies, and MET antibody-drug conjugates now play important roles in the standard treatment of MET-altered NSCLC; they have considerably improved the outcomes of patients with tumors that harbor MET oncogenic drivers. Although clinical agents are currently available and numerous other options are in development, particular challenges in the field require attention. For example, the therapeutic efficacy of each drug remains unsatisfactory, and concomitantly, the resistance mechanisms are not fully understood. Thus, there is an urgent need for optimal drug sequencing and combinations, along with a thorough understanding of treatment resistance. In this review, we describe the current landscape of pertinent clinical trials focusing on MET-targeted strategies and discuss future developmental directions in this rapidly expanding field.

Antibody-Drug Conjugates: The Dynamic Evolution from Conventional to Next-Generation Constructs

Introduced almost two decades ago, ADCs have marked a breakthrough in the targeted therapy era, providing clinical benefits to many cancer patients. While the inherent complexity of this class of drugs has challenged their development and broad application, the experience gained from years of trials and errors and recent advances in construct design and delivery have led to an increased number of ADCs approved or in late clinical development in only five years. Target and payload diversification, along with novel conjugation and linker technologies, are at the forefront of next-generation ADC development, renewing hopes to broaden the scope of these targeted drugs to difficult-to-treat cancers and beyond. This review highlights recent trends in the ADC field, focusing on construct design and mechanism of action and their implications on ADCs' therapeutic profile. The evolution from conventional to innovative ADC formats will be illustrated, along with some of the current hurdles, including toxicity and drug resistance. Future directions to improve the design of next-generation ADCs will also be presented.

The promise and challenges of combination therapies with antibody-drug conjugates in solid tumors

Antibody-drug conjugates (ADCs) represent an important class of cancer therapies that have revolutionized the treatment paradigm of solid tumors. To date, many ongoing studies of ADC combinations with a variety of anticancer drugs, encompassing chemotherapy, molecularly targeted agents, and immunotherapy, are being rigorously conducted in both preclinical studies and clinical trial settings. Nevertheless, combination therapy does not always guarantee a synergistic or additive effect and may entail overlapping toxicity risks. Therefore, understanding the current status and underlying mechanisms of ADC combination therapy is urgently required. This comprehensive review analyzes existing evidence concerning the additive or synergistic effect of ADCs with other classes of oncology medicines. Here, we discuss the biological mechanisms of different ADC combination therapy strategies, provide prominent examples, and assess their benefits and challenges. Finally, we discuss future opportunities for ADC combination therapy in clinical practice.

Ex vivo mass spectrometry-based biodistribution analysis of an antibody-Resiquimod conjugate bearing a protease-cleavable and acid-labile linker

Immune-stimulating antibody conjugates (ISACs) equipped with imidazoquinoline (IMD) payloads can stimulate endogenous immune cells to kill cancer cells, ultimately inducing long-lasting anticancer effects. A novel ISAC was designed, featuring the IMD Resiquimod (R848), a tumor-targeting antibody specific for Carbonic Anhydrase IX (CAIX) and the protease-cleavable Val-Cit-PABC linker. In vitro stability analysis showed not only R848 release in the presence of the protease Cathepsin B but also under acidic conditions. The ex vivo mass spectrometry-based biodistribution data confirmed the low stability of the linker-drug connection while highlighting the selective accumulation of the IgG in tumors and its long circulatory half-life.

Reviving immunogenic cell death upon targeting TACC3 enhances T-DM1 response in HER2-positive breast cancer

Immunogenic cell death (ICD), an immune-priming form of cell death, has been shown to be induced by several different anti-cancer therapies. Despite being the first and one of the most successful antibody-drug conjugates (ADCs) approved for refractory HER2-positive breast cancer, little is known if response and resistance to trastuzumab emtansine (T-DM1) involves ICD modulation that can be leveraged to enhance T-DM1 response. Here, we report that T-DM1 induces spindle assembly checkpoint (SAC)-dependent ICD in sensitive cells by inducing eIF2α phosphorylation, surface exposure of calreticulin, ATP and HMGB1 release, and secretion of ICD-related cytokines, all of which are lost in resistance. Accordingly, an ICD-related gene signature correlates with clinical response to T-DM1-containing therapy. We found that transforming acidic coiled-coil containing 3 (TACC3) is overexpressed in T-DM1 resistant cells, and that T-DM1 responsive patients have reduced TACC3 protein while the non-responders exhibited increased TACC3 expression during T-DM1 treatment. Notably, genetic or pharmacological inhibition of TACC3 revives T-DM1-induced SAC activation and induction of ICD markers in vitro. Finally, TACC3 inhibition elicits ICD in vivo shown by vaccination assay, and it potentiates T-DM1 by inducing dendritic cell (DC) maturation and enhancing infiltration of cytotoxic T cells in the human HER2-overexpressing MMTV.f.huHER2#5 (Fo5) transgenic model. Together, our results show that ICD is a key mechanism of action of T-DM1 which is lost in resistance, and that targeting TACC3 restores T-DM1-mediated ICD and overcomes resistance.

Reinforcing the immunogenic cell death to enhance cancer immunotherapy efficacy

Immunogenic cell death (ICD) has been a revolutionary modality in cancer treatment since it kills primary tumors and prevents recurrent malignancy simultaneously. ICD represents a particular form of cancer cell death accompanied by production of damage-associated molecular patterns (DAMPs) that can be recognized by pattern recognition receptors (PRRs), which enhances infiltration of effector T cells and potentiates antitumor immune responses. Various treatment methods can elicit ICD involving chemo- and radio-therapy, phototherapy and nanotechnology to efficiently convert dead cancer cells into vaccines and trigger the antigen-specific immune responses. Nevertheless, the efficacy of ICD-induced therapies is restrained due to low accumulation in the tumor sites and damage of normal tissues. Thus, researchers have been devoted to overcoming these problems with novel materials and strategies. In this review, current knowledge on different ICD modalities, various ICD inducers, development and application of novel ICD-inducing strategies are summarized. Moreover, the prospects and challenges are briefly outlined to provide reference for future design of novel immunotherapy based on ICD effect.

Disitamab vedotin in combination with immune checkpoint inhibitors for locally and locally advanced bladder urothelial carcinoma: a two-center's real-world study

Objective: Our study aims to assess the effectiveness and safety profile of Disitamab Vedotin (DV, RC48-ADC), an innovative humanized anti-HER2 antibody conjugated with tubulin-disrupting antimitotic drug monomethyl auristatin E (MMAE) via a cleavable peptide linker. This treatment combined immune checkpoint inhibitors as part of the bladder sparing approach for selected patients suffering from locally and locally advanced bladder urothelial carcinoma. Patients and methods: We conducted a two-center, real-world study involving locally advanced urothelial carcinoma (UC) patients. Patients were classified based on HER2 expression (IHC 3+/2+/1+) or lack of HER2 expression (IHC 0). The primary endpoint was the objective response rate (ORR), assessed by the investigator following the criteria of RECIST V1.1. Secondary endpoints encompassed the pathological complete response rate (pCR), pathological partial response rate (pPR), and pathological stable disease (pSD), along with recurrence-free survival (RFS), the pathological downstaging rate, and the safety profile of the treatment. Results: In this study, nine patients were enrolled, with a median follow-up duration of 12.0 months. The overall confirmed ORR was 88.9%, Five patients achieved a complete response (CR), and three patients achieved a partial response (PR). The radiological complete response (rCR) aligned perfectly with pCR. The median radiological progression-free survival (rPFS) spanned 12.0 months (range from 8.0 to 17.0 months). One patient diagnosed with disease progression (PD) underwent a radical cystectomy. The pathological stage evolved from T2N0M0 to T3aN2M0, followed by adjuvant chemotherapy with a gemcitabine-cisplatin (GC) combination radiotherapy. At the 9-month follow-up, neither recurrence nor metastasis was observed. The rate and intensity of complications were manageable among these patients, with no evidence of grade 4 and 5 adverse events. Conclusion: The combination of DV and PD-1 demonstrated considerable activity in the objective response rate (ORR) in patients with HER2 IHC 0/1+/2+/3+ muscle-invasive bladder cancer (MIBC), along with the longest reported median radiological progression-free survival (rPFS) to date. With an extended duration of treatment, the safety profile of DV plus PD-1 was also confirmed to be manageable.

Antibody-drug conjugates come of age in oncology

Antibody-drug conjugates (ADCs) combine the specificity of monoclonal antibodies with the potency of highly cytotoxic agents, potentially reducing the severity of side effects by preferentially targeting their payload to the tumour site. ADCs are being increasingly used in combination with other agents, including as first-line cancer therapies. As the technology to produce these complex therapeutics has matured, many more ADCs have been approved or are in late-phase clinical trials. The diversification of antigenic targets as well as bioactive payloads is rapidly broadening the scope of tumour indications for ADCs. Moreover, novel vector protein formats as well as warheads targeting the tumour microenvironment are expected to improve the intratumour distribution or activation of ADCs, and consequently their anticancer activity for difficult-to-treat tumour types. However, toxicity remains a key issue in the development of these agents, and better understanding and management of ADC-related toxicities will be essential for further optimization. This Review provides a broad overview of the recent advances and challenges in ADC development for cancer treatment.

A Theranostic Approach to Imaging and Treating Melanoma with 203Pb/212Pb-Labeled Antibody Targeting Melanin

Metastatic melanoma is a deadly disease that claims thousands of lives each year despite the introduction of several immunotherapeutic agents into the clinic over the past decade, inspiring the development of novel therapeutics and the exploration of combination therapies. Our investigations target melanin pigment with melanin-specific radiolabeled antibodies as a strategy to treat metastatic melanoma. In this study, a theranostic approach was applied by first labeling a chimeric antibody targeting melanin, c8C3, with the SPECT radionuclide 203Pb for microSPECT/CT imaging of C57Bl6 mice bearing B16-F10 melanoma tumors. Imaging was followed by radioimmunotherapy (RIT), whereby the c8C3 antibody is radiolabeled with a 212Pb/212Bi "in vivo generator", which emits cytotoxic alpha particles. Using microSPECT/CT, we collected sequential images of B16-F10 murine tumors to investigate antibody biodistribution. Treatment with the 212Pb/212Bi-labeled c8C3 antibody demonstrated a dose-response in tumor growth rate in the 5-10 µCi dose range when compared to the untreated and radiolabeled control antibody and a significant prolongation in survival. No hematologic or systemic toxicity of the treatment was observed. However, administration of higher doses resulted in a biphasic tumor dose response, with the efficacy of treatment decreasing when the administered doses exceeded 10 µCi. These results underline the need for more pre-clinical investigation of targeting melanin with 212Pb-labeled antibodies before the clinical utility of such an approach can be assessed.

Preconditioning with immunogenic cell death-inducing treatments for subsequent immunotherapy

Since the dawn of anticancer immunotherapy, the clinical use of immune checkpoint inhibitors (ICI) has increased exponentially. Monoclonal antibodies targeting CTLA-4 and the PD-1/PD-L1 interaction were first introduced for the treatment of patients with unresectable melanoma. In melanoma, ICI lead to durable regression in a significant number of patients and have thus been clinically approved as a first-line treatment of advanced disease. Over the past years an increasing number of regulatory approvals have been granted for the use of ICI in patients affected by a large range of distinct carcinomas. In retrospect surprisingly, it has been discovered that particularly successful chemotherapeutic treatments are able to trigger anticancer immune responses because they induce immunogenic cell death (ICD), hence killing cancer cells in a way that they elicit an immune response against tumor-associated antigens. Logically, preclinical studies as well as clinical trials are currently exploring the possibility to combine ICD inducers with ICI to obtain optimal therapeutic effects. Here, we provide a broad overview of current strategies for the implementation of combinatorial approaches involving ICD induction followed by ICI in anticancer therapy.

Antibody-Drug Conjugates for Breast Cancer Treatment: Emerging Agents, Targets and Future Directions

To achieve the scheme of "magic bullets" in antitumor therapy, antibody-drug conjugates (ADCs) were developed. ADCs consist of antibodies targeting tumor-specific antigens, chemical linkers, and cytotoxic payloads that powerfully kill cancer cells. With the approval of ado-trastuzumab emtansine (T-DM1) and fam-trastuzumab deruxtecan (T-DXd), the therapeutic potentials of ADCs in breast cancer have come into the spotlight. Nearly 30 ADCs for breast cancer are under exploration to move targeted therapy forward. In this review, we summarize the presenting and emerging agents and targets of ADCs. The ADC structure and development history are also concluded. Moreover, the challenges faced and prospected future directions in this field are reviewed, which give insights into novel treatments with ADCs for breast cancer.

Harnessing sortase A transpeptidation for advanced targeted therapeutics and vaccine engineering

The engineering of potent prophylactic and therapeutic complexes has always required careful protein modification techniques with seamless capabilities. In this light, methods that favor unobstructed multivalent targeting and correct antigen presentations remain essential and very demanding. Sortase A (SrtA) transpeptidation has exhibited these attributes in various settings over the years. However, its applications for engineering avidity-inspired therapeutics and potent vaccines have yet to be significantly noticed, especially in this era where active targeting and multivalent nanomedications are in great demand. This review briefly presents the SrtA enzyme and its associated transpeptidation activity and describes interesting sortase-mediated protein engineering and chemistry approaches for achieving multivalent therapeutic and antigenic responses. The review further highlights advanced applications in targeted delivery systems, multivalent therapeutics, adoptive cellular therapy, and vaccine engineering. These innovations show the potential of sortase-mediated techniques in facilitating the development of simple plug-and-play nanomedicine technologies against recalcitrant diseases and pandemics such as cancer and viral infections.

Improvement strategy for immune checkpoint blockade: A focus on the combination with immunogenic cell death inducers

Cancer immunotherapies have yielded promising outcomes in various malignant tumors by blocking specific immune checkpoint molecules, such as programmed cell death 1 and cytotoxic T lymphocyte antigen 4. However, only a few patients respond to immune checkpoint blockade therapy because of the poor immunogenicity of tumor cells and immune-suppressive tumor microenvironment. Accumulating evidence suggests that chemotherapeutic agents, including oxaliplatin and doxorubicin, not only mediate direct cytotoxicity in tumor cells but also induce immunogenic cancer cell death to stimulate a powerful anti-cancer immune response in the tumor microenvironment. In this review, we summarize the recent advances in cancer combination therapy based on immune checkpoint inhibitors plus immunogenic cell death inducers. Despite some clinical failures and challenges, immunogenic cell death inducers have displayed great potential when combined with immune checkpoint inhibitors for anti-cancer treatment in both preclinical studies and clinical trials.

Antibody-drug conjugates: in search of partners of choice

Antibody-drug conjugates (ADCs) have become a credentialled class of anticancer drugs for both solid and hematological malignancies, with regulatory approvals mainly as single agents. Despite extensive preclinical and clinical efforts to develop rational ADC-based combinations, to date only a limited number have demonstrated survival improvements over standard of care. The most appealing partners for ADCs are those that offer additive or synergistic effects on tumor cells or their microenvironment without unacceptable overlapping toxicities. Coadministration with antiangiogenic compounds, HER2-targeting drugs, DNA-damage response agents and immune checkpoint inhibitors (ICIs) represent active forerunners. Through the identification of targets with tumor-specific expression, improved conjugation technologies, and novel linkers and payloads offering superior therapeutic indices, the next generation of ADCs brings optimism to combinatorial approaches.

Immunogenic cell death in cancer: concept and therapeutic implications

Mammalian cells responding to specific perturbations of homeostasis can undergo a regulated variant of cell death that elicits adaptive immune responses. As immunogenic cell death (ICD) can only occur in a precise cellular and organismal context, it should be conceptually differentiated from instances of immunostimulation or inflammatory responses that do not mechanistically depend on cellular demise. Here, we critically discuss key conceptual and mechanistic aspects of ICD and its implications for cancer (immuno)therapy.

A potential platform of combining sialic acid derivative-modified paclitaxel cationic liposomes with antibody-drug conjugates inspires robust tumor-specific immunological memory in solid tumors

The recent approvals for antibody-drug conjugates (ADCs) in multiple malignancies in the past few years have fueled the ongoing development of this class of drug. However, the limitation of ADCs is selectivity toward cancer cells especially overexpressing the antigen of interest. To broaden the anti-cancer spectrum of ADCs, combinatorial strategies of ADCs with chemotherapy have become a central focus of the current preclinical and clinical research. Here, we used the microtubule stabilizer paclitaxel and enfortumab vedotin-ejfv (EV), an ADC carrying the microtubule inhibitor payload monomethyl auristatin E (MMAE), for co-administration under the consideration of their mechanism of action associated with microtubules. We designed a sialic acid-cholesterol (SA-CH) conjugate-modified cationic liposome platform loaded with PTX (PTX-SAL) for efficiently targeting tumor-associated immune cells. Compared with monotherapy, PTX-SAL-mediated combination therapy with ADCs significantly inhibited S180 tumor growth in mice, with complete tumor regression occurring. The formation of a durable tumor-specific immunological memory response in mice that experienced complete tumor regression was assessed by secondary tumor cell rechallenge, and the production of memory T cells in the spleen was detected as related to the increased CD4⁺T memory cells and the enhanced serum IFN-γ. All our preliminary results throw light on the tremendous application potential for the application of this combination therapy regimen capable of mounting a durable immune response and stimulating a robust T cell-mediated tumor-specific immunological memory.

Payload diversification: a key step in the development of antibody-drug conjugates

Antibody-drug conjugates (ADCs) is a fast moving class of targeted biotherapeutics that currently combines the selectivity of monoclonal antibodies with the potency of a payload consisting of cytotoxic agents. For many years microtubule targeting and DNA-intercalating agents were at the forefront of ADC development. The recent approval and clinical success of trastuzumab deruxtecan (Enhertu^®) and sacituzumab govitecan (Trodelvy^®), two topoisomerase 1 inhibitor-based ADCs, has shown the potential of conjugating unconventional payloads with differentiated mechanisms of action. Among future developments in the ADC field, payload diversification is expected to play a key role as illustrated by a growing number of preclinical and clinical stage unconventional payload-conjugated ADCs. This review presents a comprehensive overview of validated, forgotten and newly developed payloads with different mechanisms of action.

Antibody-Drug Conjugates: A New Therapeutic Approach for Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subset associated with a worse prognosis and poor response to conventional chemotherapy. Despite recent advances in drug discovery, its management is still a challenge for clinicians, illuminating the unmet need to develop novel treatment approaches. Antibody-drug conjugates (ADC) are innovative oncology drugs that combine the specificity of monoclonal antibodies and the high efficacy of anticancer payloads, to deliver cytotoxic drugs selectively to cancer cells. Various ADCs were investigated for TNBC and have provided a promise for this aggressive women's cancer including the FDA-approved sacituzumab govitecan. In this chapter, we reviewed different ADCs studied for TNBC including their mechanisms of action, efficacy, and tolerability. Moreover, we have also discussed their therapeutic potential based on combinatorial approaches with other targeted therapies in early and metastatic TNBC.

Syngeneic mouse model of human HER2+ metastatic breast cancer for the evaluation of trastuzumab emtansine combined with oncolytic rhabdovirus

Background

Established mouse models of HER2+ cancer are based on the over-expression of rodent Neu/Erbb2 homologues, which are incompatible with human HER2 (huHER2) targeted therapeutics. Additionally, the use of immune-deficient xenograft or transgenic models precludes assessment of native anti-tumour immune responses. These hurdles have been a challenge for our understanding of the immune mechanisms behind huHER2-targeting immunotherapies.

Methods

To assess the immune impacts of our huHER2-targeted combination strategy, we generated a syngeneic mouse model of huHER2+ breast cancer, using a truncated form of huHER2, HER2T. Following validation of this model, we next treated tumour-bearing with our immunotherapy strategy: oncolytic vesicular stomatitis virus (VSVΔ51) with clinically approved antibody-drug conjugate targeting huHER2, trastuzumab emtansine (T-DM1). We assessed efficacy through tumour control, survival, and immune analyses.

Results

The generated truncated HER2T construct was non-immunogenic in wildtype BALB/c mice upon expression in murine mammary carcinoma 4T1.2 cells. Treatment of 4T1.2-HER2T tumours with VSVΔ51+T-DM1 yielded robust curative efficacy compared to controls, and broad immunologic memory. Interrogation of anti-tumour immunity revealed tumour infiltration by CD4+ T cells, and activation of B, NK, and dendritic cell responses, as well as tumour-reactive serum IgG.

Conclusions

The 4T1.2-HER2T model was used to evaluate the anti-tumour immune responses following our complex pharmacoviral treatment strategy. These data demonstrate utility of the syngeneic HER2T model for assessment of huHER2-targeted therapies in an immune-competent in vivo setting. We further demonstrated that HER2T can be implemented in multiple other syngeneic tumour models, including but not limited to colorectal and ovarian models. These data also suggest that the HER2T platform may be used to assess a range of surface-HER2T targeting approaches, such as CAR-T, T-cell engagers, antibodies, or even retargeted oncolytic viruses.

Immunosuppressive tumor microenvironment modulation by chemotherapies and targeted therapies to enhance immunotherapy effectiveness

With the rapid clinical development of immune checkpoint inhibitors (ICIs), the standard of care in cancer management has evolved rapidly. However, immunotherapy is not currently beneficial for all patients. In addition to intrinsic tumor factors, other etiologies of resistance to ICIs arise from the complex interplay between cancer and its microenvironment. Recognition of the essential role of the tumor microenvironment (TME) in cancer progression has led to a shift from a tumor-cell-centered view of cancer development, to the concept of a complex tumor ecosystem that supports tumor growth and metastatic dissemination. The expansion of immunosuppressive cells represents a cardinal strategy deployed by tumor cells to escape detection and elimination by the immune system. Regulatory T lymphocytes (Treg), myeloid-derived suppressor cells (MDSCs), and type-2 tumor-associated macrophages (TAM2) are major components of these inhibitory cellular networks, with the ability to suppress innate and adaptive anticancer immunity. They therefore represent major impediments to anticancer therapies, particularly immune-based interventions. Recent work has provided evidence that, beyond their direct cytotoxic effects on cancer cells, several conventional chemotherapeutic (CT) drugs and agents used in targeted therapies (TT) can promote the elimination or inactivation of suppressive immune cells, resulting in enhanced antitumor immunity. In this review, we will analyze findings pertaining to this concept, discuss the possible molecular bases underlying the selective targeting of these immunosuppressive cells by antineoplastic agents (CT and/or TT), and consider current challenges and future prospects related to the integration of these molecules into more efficient anticancer strategies, in the era of immunotherapy.

Identification and Validation of Novel Immunogenic Cell Death- and DNA Damage Response-Related Molecular Patterns Correlated with Immune Status and Prognosis in Hepatocellular Carcinoma

Immunogenic cell death (ICD) and DNA damage response (DDR) are involved in cancer progression and prognosis. Currently, chemotherapy is the first-line treatment for intermediate or advanced hepatocellular carcinoma (HCC), which is mostly based on platinum and anthracyclines that induce DNA damage and ICD. With the treatment of HCC with immune checkpoint inhibitors (ICIs), it is important to understand the molecular characteristics and prognostic values of ICD and DDR-related genes (IDRGs). We aimed to explore the characteristics of ICD and DDR-related molecular patterns, immune status, and the association of immunotherapy and prognosis with IDRGs in HCC. We identified IDRGs in HCC and evaluated their differential expression, biological behaviors, molecular characteristics, immune cell infiltration, and prognostic value. Prognostic IDRGs and subtypes were identified and validated. FFAR3, DDX1, POLR3G, FANCL, ADA, PI3KR1, DHX58, TPT1, MGMT, SLAMF6, and EIF2AK4 were determined as risk factors for HCC, and the biological experiments indicated that high FANCL expression is harmful to the treatment and prognosis. HCC was classified into high- and low-risk groups based on the median values of the risk factors to construct a predictive nomogram. These findings provide novel insights into the treatment and prognosis of HCC and provide a new research direction for HCC.

GPC2 antibody-drug conjugate reprograms the neuroblastoma immune milieu to enhance macrophage-driven therapies

BACKGROUND

Antibody-drug conjugates (ADCs) that deliver cytotoxic drugs to tumor cells have emerged as an effective and safe anticancer therapy. ADCs may induce immunogenic cell death (ICD) to promote additional endogenous antitumor immune responses. Here, we characterized the immunomodulatory properties of D3-GPC2-PBD, a pyrrolobenzodiazepine (PBD) dimer-bearing ADC that targets glypican 2 (GPC2), a cell surface oncoprotein highly differentially expressed in neuroblastoma.

METHODS

ADC-mediated induction of ICD was studied in GPC2-expressing murine neuroblastomas in vitro and in vivo. ADC reprogramming of the neuroblastoma tumor microenvironment was profiled by RNA sequencing, cytokine arrays, cytometry by time of flight and flow cytometry. ADC efficacy was tested in combination with macrophage-driven immunoregulators in neuroblastoma syngeneic allografts and human patient-derived xenografts.

RESULTS

The D3-GPC2-PBD ADC induced biomarkers of ICD, including neuroblastoma cell membrane translocation of calreticulin and heat shock proteins (HSP70/90) and release of high-mobility group box 1 and ATP. Vaccination of immunocompetent mice with ADC-treated murine neuroblastoma cells promoted T cell-mediated immune responses that protected animals against tumor rechallenge. ADC treatment also reprogrammed the tumor immune microenvironment to a proinflammatory state in these syngeneic neuroblastoma models, with increased tumor trafficking of activated macrophages and T cells. In turn, macrophage or T-cell inhibition impaired ADC efficacy in vivo, which was alternatively enhanced by both CD40 agonist and CD47 antagonist antibodies. In human neuroblastomas, the D3-GPC2-PBD ADC also induced ICD and promoted tumor phagocytosis by macrophages, which was further enhanced when blocking CD47 signaling in vitro and in vivo.

CONCLUSIONS

We elucidated the immunoregulatory properties of a GPC2-targeted ADC and showed robust efficacy of combination immunotherapies in diverse neuroblastoma preclinical models.

Antibody drug conjugates targeting HER2: Clinical development in metastatic breast cancer

The identification of the HER2 alteration as an actionable oncogenic driver in breast cancer has propelled the development of HER-targeting monoclonal antibodies (mAb) such as trastuzumab and pertuzumab, which led to dramatic improvements in survival outcomes. Lately, the great strides made toward developing antibody-conjugation methods have led to the development of a new class of compelling compounds, the antibody-drug conjugates (ADCs) targeting HER2 which have profoundly transformed the treatment landscape of breast cancer. HER2-targeting ADCs, trastuzumab-emtansine and trastuzumab-deruxtecan, have improved the overall survival in the second and third-line settings with manageable adverse events. Other HER2-targeting ADCs using novel technological advances in the antibody, linker and/or payload conception have shown promising activity in preclinical and clinical studies and some of them are now being evaluated in larger clinical trials. Multiple challenges still impede the success of ADCs in breast cancer namely the lack of a comprehensive understanding of resistance mechanisms as well as the mechanisms of action of ADCs in special subgroups of patients such as those with low or ultra-low HER2 expression and patients with brain or leptomeningeal metastases (BM). In this framework, we review the approved indications and ongoing trials for HER2-targeting ADCs, across patient subgroups, including those with BM and discuss the associated potential mechanisms of action and resistance. Last, we provide an overview of the future perspectives involving HER2-targeting ADCs in breast cancer.

Targeting cancer glycosylation repolarizes tumor-associated macrophages allowing effective immune checkpoint blockade

Immune checkpoint blockade (ICB) has substantially improved the prognosis of patients with cancer, but the majority experiences limited benefit, supporting the need for new therapeutic approaches. Up-regulation of sialic acid-containing glycans, termed hypersialylation, is a common feature of cancer-associated glycosylation, driving disease progression and immune escape through the engagement of Siglec receptors on tumor-infiltrating immune cells. Here, we show that tumor sialylation correlates with distinct immune states and reduced survival in human cancers. The targeted removal of Siglec ligands in the tumor microenvironment, using an antibody-sialidase conjugate, enhanced antitumor immunity and halted tumor progression in several murine models. Using single-cell RNA sequencing, we revealed that desialylation repolarized tumor-associated macrophages (TAMs). We also identified Siglec-E as the main receptor for hypersialylation on TAMs. Last, we found that genetic and therapeutic desialylation, as well as loss of Siglec-E, enhanced the efficacy of ICB. Thus, therapeutic desialylation represents an immunotherapeutic approach to reshape macrophage phenotypes and augment the adaptive antitumor immune response.

Combinatorial regimens of chemotherapeutic agents: A new perspective on raising the heat of the tumor immune microenvironment

Harnessing the broad immunostimulatory capabilities of chemotherapy in combination with immune checkpoint inhibitors has improved immunotherapy outcomes in patients with cancer. Certain chemotherapeutic agents can extensively modify the tumor microenvironment (TME), resulting in the reprogramming of local immune responses. Although chemotherapeutic agents with an enhanced generation of potent anti-tumor immune responses have been tested in preclinical animal models and clinical trials, this strategy has not yet shown substantial therapeutic efficacy in selected difficult-to-treat cancer types. In addition, the efficacy of chemotherapeutic agent-based monotherapy in eliciting a long-term anti-tumor immune response is restricted by the immunosuppressive TME. To enhance the immunomodulatory effect of chemotherapy, researchers have made many attempts, mainly focusing on improving the targeted distribution of chemotherapeutic agents and designing combination therapies. Here, we focused on the mechanisms of the anti-tumor immune response to chemotherapeutic agents and enumerated the attempts to advance the use of chemo-immunotherapy. Furthermore, we have listed the important considerations in designing combinations of these drugs to maximize efficacy and improve treatment response rates in patients with cancer.

Disulfiram/Copper Induces Immunogenic Cell Death and Enhances CD47 Blockade in Hepatocellular Carcinoma

Some chemotherapeutic agents have been found to enhance antitumor immunity by inducing immunogenic cell death (ICD). The combination of disulfiram (DSF) and copper (Cu) has demonstrated anti-tumor effects in a range of malignancies including hepatocellular carcinoma (HCC). However, the potential of DSF/Cu as an ICD inducer and whether it can enhance the efficacy of the immune checkpoint blockade in HCC remains unknown. Here, we showed that DSF/Cu-treated HCC cells exhibited characteristics of ICD in vitro, such as calreticulin (CRT) exposure, ATP secretion, and high mobility group box 1 (HMGB1) release. DSF/Cu-treated HCC cells elicited significant immune memory in a vaccination assay. DSF/Cu treatment promoted dendritic cell activation and maturation. The combination of DSF/Cu and CD47 blockade further facilitated DC maturation and subsequently enhanced CD8+ T cell cytotoxicity. Mechanically, DSF/Cu promoted the nuclear accumulation and aggregation of nuclear protein localization protein 4 (NPL4) to inhibit the ubiquitin-proteasome system; thus, inducing endoplasmic reticulum (ER) stress. The inhibition of NPL4 induced ICD-associated damage-associated molecular patterns. Collectively, our findings demonstrated that DSF/Cu-induced ICD-mediated immune activation in HCC enhanced the efficacy of CD47 blockade.

Immunogenic Cell Death Enhances Immunotherapy of Diffuse Intrinsic Pontine Glioma: From Preclinical to Clinical Studies

Diffuse intrinsic pontine glioma (DIPG) is the most lethal tumor involving the pediatric central nervous system. The median survival of children that are diagnosed with DIPG is only 9 to 11 months. More than 200 clinical trials have failed to increase the survival outcomes using conventional cytotoxic or myeloablative chemotherapy. Immunotherapy presents exciting therapeutic opportunities against DIPG that is characterized by unique and heterogeneous features. However, the non-inflammatory DIPG microenvironment greatly limits the role of immunotherapy in DIPG. Encouragingly, the induction of immunogenic cell death, accompanied by the release of damage-associated molecular patterns (DAMPs) shows satisfactory efficacy of immune stimulation and antitumor strategies. This review dwells on the dilemma and advances in immunotherapy for DIPG, and the potential efficacy of immunogenic cell death (ICD) in the immunotherapy of DIPG.

NK cells with tissue-resident traits shape response to immunotherapy by inducing adaptive antitumor immunity

T cell–directed cancer immunotherapy often fails to generate lasting tumor control. Harnessing additional effectors of the immune response against tumors may strengthen the clinical benefit of immunotherapies. Here, we demonstrate that therapeutic targeting of the interferon-γ (IFN-γ)–interleukin-12 (IL-12) pathway relies on the ability of a population of natural killer (NK) cells with tissue-resident traits to orchestrate an antitumor microenvironment. In particular, we used an engineered adenoviral platform as a tool for intratumoral IL-12 immunotherapy (AdV5–IL-12) to generate adaptive antitumor immunity. Mechanistically, we demonstrate that AdV5–IL-12 is capable of inducing the expression of CC-chemokine ligand 5 (CCL5) in CD49a + NK cells both in tumor mouse models and tumor specimens from patients with cancer. AdV5–IL-12 imposed CCL5-induced type I conventional dendritic cell (cDC1) infiltration and thus increased DC-CD8 T cell interactions. A similar observation was made for other IFN-γ–inducing therapies such as Programmed cell death 1 (PD-1) blockade. Conversely, failure to respond to IL-12 and PD-1 blockade in tumor models with low CD49a + CXCR6 + NK cell infiltration could be overcome by intratumoral delivery of CCL5. Thus, therapeutic efficacy depends on the abundance of NK cells with tissue-resident traits and, specifically, their capacity to produce the DC chemoattractant CCL5. Our findings reveal a barrier for T cell–focused therapies and offer mechanistic insights into how T cell–NK cell–DC cross-talk can be enhanced to promote antitumor immunity and overcome resistance.

Disitamab vedotin: a novel antibody-drug conjugates for cancer therapy

Human epidermal growth factor receptor 2 (HER2) regulates cell mitosis, proliferation, and apoptosis. Trastuzumab is a HER2-targeted monoclonal antibody (mAB), which can prolong the overall survival rate of patients with HER2 overexpression in later periods of gastric cancer and breast cancer. Although anti-HER2 monoclonal antibody has a curative effect, adjuvant chemotherapy is still necessary to upgrade the curative effect maximumly. Antibody-drug conjugate (ADC) is a kind of therapeutic drug that contains antigen-specific antibody and cytotoxic payload, which can improve the survival time of tumor patients. To date, there are several HER2-ADC products on the market, for which two anti-HER2 ADC (trastuzumab emtansine and trastuzumab deruxtecan) have been authorized by the FDA for distinct types of HER2-positive carcinoma in the breast. Disitamab vedotin (RC48) is a newly developed ADC drug targeting HER2 that is comprised of hertuzumab coupling monomethyl auristatin E (MMAE) via a cleavable linker. This paper aims to offer a general insight and summary of the mechanism of action and the currently completed and ongoing clinical studies of RC-48 in HER-2 positive solid tumors.

Antibody-drug conjugate as targeted therapeutics against hepatocellular carcinoma: preclinical studies and clinical relevance

An antibody-drug conjugate (ADC) is an advanced chemotherapeutic option with immense promises in treating many tumor. They are designed to selectively attack and kill neoplastic cells with minimal toxicity to normal tissues. ADCs are complex engineered immunoconjugates that comprise a monoclonal antibody for site-directed delivery and cytotoxic payload for targeted destruction of malignant cells. Therefore, it enables the reduction of off-target toxicities and enhances the therapeutic index of the drug. Hepatocellular carcinoma (HCC) is a solid tumor that shows high heterogeneity of molecular phenotypes and is considered the second most common cause of cancer-related death. Studies show enormous potential for ADCs targeting GPC3 and CD24 and other tumor-associated antigens in HCC with their high, selective expression and show potential outputs in preclinical evaluations. The review mainly highlights the preclinical evaluation of different antigen-targeted ADCs such as MetFab-DOX, Anti-c-Met IgG-OXA, Anti CD 24, ANC-HN-01, G7mab-DOX, hYP7-DCand hYP7-PC, Anti-CD147 ILs-DOX and AC133-vcMMAF against hepatocellular carcinoma and its future relevance.

Antibody–drug conjugates harboring a kinesin spindle protein inhibitor with immunostimulatory properties

Antibody–drug conjugates (ADCs) are used to target cancer cells by means of antibodies directed to tumor-associated antigens, causing the incorporation of a cytotoxic payload into target cells. Here, we characterized the mode of action of ADC costing of a TWEAKR-specific monoclonal antibody conjugated to a small molecule kinesin spindle protein (KSP) inhibitor (KSPi). These TWEAKR-KSPi-ADCs showed strong efficacy in a TWEAKR expressing CT26 colon cancer model in mice. TWEAKR-KSPi-ADCs controlled the growth of CT26 colon cancers in immunodeficient as well as in immunocompetent mice. However, when treated with suboptimal doses, TWEAKR-KSPi-ADCs were still active in immunocompetent but not in immunodeficient mice, indicating that TWEAKR-KSPi-ADCs act – in addition to the cytotoxic mode of action – through an immunological mechanism. Indeed, in vitro experiments performed with a cell-permeable small molecule KSPi closely related to the active payload released from the TWEAKR-KSPi-ADCs revealed that KSPi was capable of stimulating several hallmarks of immunogenic cell death (ICD) on three different human cancer cell lines: cellular release of adenosine triphosphate (ATP) and high mobility group B1 protein (HMGB1), exposure of calreticulin on the cell surface as well as a transcriptional type-I interferon response. Further, in vivo experiments confirmed that treatment with TWEAKR-KSPi-ADCs activated immune responses via enhancing the infiltration of CD4⁺ and CD8⁺ T lymphocytes in tumors and the local production of interferon-γ, interleukin-2, and tumor necrosis factor-α. In conclusion, the antineoplastic effects of TWEAKR-KSPi-ADCs can partly be attributed to its ICD-stimulatory properties.

Combination therapy with immune checkpoint inhibitors (ICIs); a new frontier

Recently, immune checkpoint inhibitors (ICIs) therapy has become a promising therapeutic strategy with encouraging therapeutic outcomes due to their durable anti-tumor effects. Though, tumor inherent or acquired resistance to ICIs accompanied with treatment-related toxicities hamper their clinical utility. Overall, about 60-70% of patients (e.g., melanoma and lung cancer) who received ICIs show no objective response to intervention. The resistance to ICIs mainly caused by alterations in the tumor microenvironment (TME), which in turn, supports angiogenesis and also blocks immune cell antitumor activities, facilitating tumor cells' evasion from host immunosurveillance. Thereby, it has been supposed and also validated that combination therapy with ICIs and other therapeutic means, ranging from chemoradiotherapy to targeted therapies as well as cancer vaccines, can capably compromise tumor resistance to immune checkpoint blocked therapy. Herein, we have focused on the therapeutic benefits of ICIs as a groundbreaking approach in the context of tumor immunotherapy and also deliver an overview concerning the therapeutic influences of the addition of ICIs to other modalities to circumvent tumor resistance to ICIs.

Simulating the Selection of Resistant Cells with Bystander Killing and Antibody Coadministration in Heterogeneous Human Epidermal Growth Factor Receptor 2-Positive Tumors

Intratumoral heterogeneity is a leading cause of treatment failure resulting in tumor recurrence. For the antibody-drug conjugate (ADC) ado-trastuzumab emtansine (T-DM1), two major types of resistance include changes in human epidermal growth factor receptor 2 (HER2) expression and reduced payload sensitivity, which is often exacerbated by heterogenous HER2 expression and ADC distribution during treatment. ADCs with bystander payloads, such as trastuzumab-monomethyl auristatin E (T-MMAE), can reach and kill adjacent cells with lower receptor expression that cannot be targeted directly with the ADC. Additionally, coadministration of T-DM1 with its unconjugated antibody, trastuzumab, can improve distribution and minimize heterogeneous delivery. However, the effectiveness of trastuzumab coadministration and ADC bystander killing in heterogenous tumors in reducing the selection of resistant cells is not well understood. Here, we use an agent-based model to predict outcomes with these different regimens. The simulations demonstrate that both T-DM1 and T-MMAE benefit from trastuzumab coadministration for tumors with high average receptor expression (up to 70% and 40% decrease in average tumor volume, respectively), with greater benefit for nonbystander payloads. However, the benefit decreases as receptor expression is reduced, reversing at low concentrations (up to 360% and 430% increase in average tumor volume for T-DM1 and T-MMAE, respectively) for this mechanism that impacts both ADC distribution and efficacy. For tumors with intrinsic payload resistance, coadministration uniformly exhibits better efficacy than ADC monotherapy (50%-70% and 19%-36% decrease in average tumor volume for T-DM1 and T-MMAE, respectively). Finally, we demonstrate that several regimens select for resistant cells at clinical tolerable doses, which highlights the need to pursue other mechanisms of action for durable treatment responses. SIGNIFICANCE STATEMENT: Experimental evidence demonstrates heterogeneity in the distribution of both the antibody-drug conjugate and the target receptor in the tumor microenvironment, which can promote the selection of resistant cells and lead to recurrence. This study quantifies the impact of increasing the antibody dose and utilizing bystander payloads in heterogeneous tumors. Alternative cell-killing mechanisms are needed to avoid enriching resistant cell populations.

Novel ADCs and Strategies to Overcome Resistance to Anti-HER2 ADCs

During recent years, a number of new compounds against HER2 have reached clinics, improving the prognosis and quality of life of HER2-positive breast cancer patients. Nonetheless, resistance to standard-of-care drugs has motivated the development of novel agents, such as new antibody-drug conjugates (ADCs). The latter are a group of drugs that benefit from the potency of cytotoxic agents whose action is specifically guided to the tumor by the target-specific antibody. Two anti-HER2 ADCs have reached the clinic: trastuzumab-emtansine and, more recently, trastuzumab-deruxtecan. In addition, several other HER2-targeted ADCs are in preclinical or clinical development, some of them with promising signs of activity. In the present review, the structure, mechanism of action, and potential resistance to all these ADCs will be described. Specific attention will be given to discussing novel strategies to circumvent resistance to ADCs.

Therapeutic Associations Comprising Anti-PD-1/PD-L1 in Breast Cancer: Clinical Challenges and Perspectives

Despite a few cases of long-responder patients, immunotherapy with anti-PD-(L)1 has so far proved rather disappointing in monotherapy in metastatic breast cancer, prompting the use of synergistic therapeutic combinations incorporating immunotherapy by immune-checkpoint inhibitors. In addition, a better understanding of both the mechanisms of sensitivity and resistance to immunotherapy, as well as the immunological effects of the usual treatments for breast cancer, make it possible to rationally consider this type of therapeutic combination. For several years, certain treatments, commonly used to treat patients with breast cancer, have shown that in addition to their direct cytotoxic effects, they may have an impact on the tumor immune microenvironment, by increasing the antigenicity and/or immunogenicity of a "cold" tumor, targeting the immunosuppressive microenvironment or counteracting the immune-exclusion profile. This review focuses on preclinical immunologic synergic mechanisms of various standard therapeutic approaches with anti-PD-(L)1, and discusses the potential clinical use of anti-PD-1/L1 combinations in metastatic or early breast cancer.

Perspectives on the development of antibody-drug conjugates targeting ROR1 for hematological and solid cancers

Antibody–drug conjugates (ADCs) are targeted therapeutics generated by conjugation of cytotoxic small molecules to monoclonal antibodies (mAbs) via chemical linkers. Due to their selective delivery of toxic payloads to antigen-positive cancer cells, ADCs demonstrate wider therapeutic indexes compared with conventional chemotherapy. After decades of intensive research and development, significant advances have been made in the field, leading to a total of 10 U.S. food and drug administration (FDA)-approved ADCs to treat cancer patients. Currently, ~80 ADCs targeting different antigens are under clinical evaluation for treatment of either hematological or solid malignancies. Notably, three ADCs targeting the same oncofetal protein, receptor tyrosine kinase like orphan receptor 1 (ROR1), have attracted considerable attention when they were acquired or licensed successively in the fourth quarter of 2020 by three major pharmaceutical companies. Apparently, ROR1 has emerged as an attractive target for cancer therapy. Since all the components of ADCs, including the antibody, linker and payload, as well as the conjugation method, play critical roles in ADC’s efficacy and performance, their choice and combination will determine how far they can be advanced. This review summarizes the design and development of current anti-ROR1 ADCs and highlights an emerging trend to target ROR1 for cancer therapy.

Targeting the DNA damage response in immuno-oncology: developments and opportunities

Immunotherapy has revolutionized cancer treatment and substantially improved patient outcome with regard to multiple tumour types. However, most patients still do not benefit from such therapies, notably because of the absence of pre-existing T cell infiltration. DNA damage response (DDR) deficiency has recently emerged as an important determinant of tumour immunogenicity. A growing body of evidence now supports the concept that DDR-targeted therapies can increase the antitumour immune response by (1) promoting antigenicity through increased mutability and genomic instability, (2) enhancing adjuvanticity through the activation of cytosolic immunity and immunogenic cell death and (3) favouring reactogenicity through the modulation of factors that control the tumour-immune cell synapse. In this Review, we discuss the interplay between the DDR and anticancer immunity and highlight how this dynamic interaction contributes to shaping tumour immunogenicity. We also review the most innovative preclinical approaches that could be used to investigate such effects, including recently developed ex vivo systems. Finally, we highlight the therapeutic opportunities presented by the exploitation of the DDR-anticancer immunity interplay, with a focus on those in early-phase clinical development.

Anticancer Activity of Biogenic Selenium Nanoparticles: Apoptotic and Immunogenic Cell Death Markers in Colon Cancer Cells

Colorectal cancer is a health problem with high mortality rates and prevalence. Thus, innovative treatment approaches need to be developed. Biogenic nanoparticles are nanomaterials that can be synthesised in biological systems and, compared to chemically synthesised nanoparticles, have better bioavailability while being more cost-effective, eco-friendlier, and less toxic. In our previous studies, the probiotic strain Lactobacillus casei ATCC 393 was used to synthesise selenium nanoparticles (SeNps), which were shown to inhibit colon cancer cell growth in vitro and in vivo. Herein, we have further investigated SeNps' pro-apoptotic activity and their ability to induce immunogenic cell death (ICD) in colon cancer cells. The SeNps' effect on Caco-2 cells growth was examined along with their potential to induce caspase activation. Moreover, the expression of typical pro-apoptotic and ICD markers were examined in SeNps-treated HT29 and CT26 cells by flow cytometry, Western blot, ELISA and fluorescence microscopy. Elevated caspase-3 activation and surface phosphatyldoserine, that subsided upon co-incubation with a pan-caspase inhibitor, were detected in SeNps-treated cells. Furthermore, nanoparticles induced modulation of the expression of various apoptosis-related proteins. We also report the detection of biomarkers involved in ICD, namely the translocation of calreticulin and ERp57, the release of HMGB1 and ATP, and the secretion of pro-inflammatory cytokines from SeNps-treated cells. Moreover, RAW246.7 macrophages exhibited a higher rate of phagocytosis against treated CT26 when compared to control cells. Taken together, our findings indicate that treatment with SeNps might be an efficient strategy to destroy tumour cells by inducing apoptotic cell death and triggering immune responses.

Antibody drug conjugates in gastrointestinal cancer: From lab to clinical development

The antibody-drug conjugates (ADCs) are one the fastest growing biotherapeutics in oncology and are still in their infancy in gastrointestinal (GI) cancer for clinical applications to improve patient survival. The ADC based approach is developed with tumor specific antigen, antibody carrying cytotoxic agents to precisely target and deliver chemotherapeutics at the tumor site. To date, 11 ADCs have been approved by US-FDA, and more than 80 are in the clinical development phase for different oncological indications. However, The ADCs based therapies in GI cancers are still far from having high-efficient clinical outcomes. The limited success of these ADCs and lessons learned from the past are now being used to develop a newer generation of ADC against GI cancers. In this review, we did a comprehensive assessment of the key components of ADCs, including tumor marker, antibody, cytotoxic payload, and linkage strategy, with a focus on technical improvement and some future trends in the pipeline for clinical translation. The various preclinical and clinical ADCs used in gastrointestinal malignancies, their target, composition and bioconjugation, along with preclinical and clinical outcomes, are discussed. The emphasis is also given to new generation ADCs employing novel mAb, payload, linker, and bioconjugation methods are also included.