Subsequent Rechallenge Research Articles

IMMU-72. TYPE I INTERFERON SIGNALING WITHIN GLIOBLASTOMA CELLS PROMOTES T-CELL EXHAUSTION AND RESISTANCE TO CHECKPOINT INHIBITORS

Abstract Glioblastoma (GBM) remains among the most fatal cancers with few treatment modalities and resistance to modern immunotherapeutic treatment paradigms including immune checkpoint inhibitors (ICI). ICIs neutralize the regulatory signals that disable T cells and have demonstrated remarkable efficacy against a variety of cancers, though not in GBM. The impotence of ICI in GBM has been linked to the tumor’s remarkable capacity to elicit T cell exhaustion, though the mechanism remains poorly understood. Chronic interferon (IFN) cytokine signaling is known to promote immunosuppression and Tex in several cancer types as well as resistance to ICI. However, the role of IFN in GBM has not been investigated despite evidence that IFN signatures exist within clinical samples of GBM. Syngeneic murine GBM cell lines CT2A and SB28 were utilized for in vivo and in vitro studies. Anti-mouse PD-1 and CD8 antibodies or PBS control were injected intraperitoneally. CRISPR editing was used to create validated knockouts (KO) of the type I IFN receptor (IFNAR1) in CT2A. Mice bearing IFNAR1 KO intracranial tumors have improved median survival (p < 0.05) and are exquisitely sensitive to checkpoint anti-PD-1 blockade (p < 0.05) with the majority of mice surviving. Furthermore, surviving mice reject the subsequent intracranial re-challenge with parental CT2A tumors compared to controls (p <0.05) suggesting central memory responses mediating rejection. We conclude that abrogation of Type I IFN signaling is sufficient to extend survival which is further enhanced by ICI. Work is ongoing to further elucidate the precise mechanism that mediates this response and to identify a therapeutic intervention that enables tumor-specific inhibition of the IFN pathway with preliminary work suggesting a CD8 T cell mediated response and reversal of the T cell exhaustion phenotype.

Plasma statin concentrations do not correlate with statin-induced myalgia

Abstract Aims Statins are essential in cardiovascular prevention. Although well-tolerated, patient adherence is often suboptimal due to experienced musculoskeletal symptoms ranging from mild myalgia to rare life-threatening rhabdomyolysis. This study aimed to investigate the relationship between plasma concentrations of statin metabolites in patients experiencing myalgia without rhabdomyolysis. Methods and results Plasma concentrations of statin metabolites were quantitatively assessed using mass spectrometry across three case-control cohorts evaluating statin-induced myalgia. The analysis included a total of 373 patients from the MILANO study (N=85 with self -reported myalgia), the MONTREAL study (N=248 with clinically verified myalgia) and the STOMP study (N=40 with rechallenge-verified statin-induced myalgia). STOMP found no significant difference in the plasma concentrations of statin metabolites between statin naïve patients with myalgia (N=12) taking atorvastatin 80 mg daily and asymptomatic controls (N=28), including upon subsequent statin rechallenge. Both the MILANO and MONTREAL studies showed lower plasma concentrations of statin metabolites in patients with myalgias compared to controls. MILANO showed a significant difference in rosuvastatin lactone concentration in patients with myalgias compared to asymptomatic controls (P = 0.025). Similarly, MONTREAL showed significantly lower mean atorvastatin metabolite concentrations in affected patients versus controls (P values ranging from 0.0073 to 0.037). Atorvastatin dosages in MONTREAL ranged from 5 to 80 mg daily, the most frequent regimens being 20 mg (27% in cases; 24% in controls) and 40 mg (33% in cases; 37% in controls). Creatine kinase levels were measured in all cohorts and were not different between cases and controls. Conclusion Development of myalgias in patients with normal creatine kinase levels is not associated with higher statin metabolite plasma concentrations. Myalgias during statin therapy are not caused by pharmacokinetic abnormalities.

Real-world data on the efficacy and safety of hedgehog pathway inhibitors in patients with basal cell carcinoma: Experience of a tertiary Australian centre.

Basal cell carcinomas (BCCs) are the most common cancers worldwide. Although most BCCs are amenable to local treatment, there are limited therapeutic options for surgically unresectable locally advanced and metastatic BCCs. Activation of the sonic hedgehog signalling pathway plays a significant role in the development of most BCCs. Hedgehog pathway inhibitors (HPIs) can be used to inhibit this pathway. Efficacy and safety data on HPI use in Australia is scarce. This study aims to present the effectiveness and safety of HPI at a tertiary dermatology referral centre. We conducted a retrospective analysis of the clinical charts of all patients with BCC treated with an HPI at a tertiary Dermatology referral centre in New South Wales, Australia from 1 January 2016 to 1 July 2023. Twenty-three patients with BCCs were treated with an HPI; 11 locally advanced, 8 multiple, 3 basal cell naevus syndrome and 1 metastatic. All patients were of Caucasian background, with a median age of 56. Across 41 treatment cycles, the median treatment duration was 4 months. The overall response rate (ORR) was 20/23 (87%) and complete response (CR) rate was 9/23 (39%); patients treated with sonidegib achieved an ORR of 11/12 (92%) and CR of 4/12 (33%), and vismodegib-treated patients achieved an ORR of 9/11 (82%) and CR of 5/11 (45%). Patients who responded to HPI treatment also responded to a subsequent HPI rechallenge. Common treatment emergent adverse events (TEAEs) included muscle spasms, dysgeusia and alopecia. Dysgeusia was more frequent with vismodegib than sonidegib (p = 0.0001). There was no evidence to suggest a difference in other TEAEs between the two HPIs. Four treatment cycles were stopped due to grade 3 muscle spasm. In our cohort of 23 patients being treated with HPI, the ORR was 87% and CR was 39%. All patients who experienced TEAEs and had a drug holiday successfully responded to HPI rechallenge.TEAEs, particularly muscle spasms, are common reasons for treatment cessation. Clinicians should implement strategies to mitigate TEAE to improve drug survivability.

Efficacy of a platinum-based chemotherapy rechallenge for platinum-sensitive recurrence after PARP inhibitor maintenance

ObjectivePlatinum-free interval (PFI) is the period from the end of platinum-based chemotherapy to the date of recurrence. If the PFI is > 6 months, a platinum-based chemotherapy rechallenge is considered; however, its efficacy after poly adenosine 5′-diphosphate-ribose polymerase (PARP) inhibitor maintenance therapy is unknown. This study aimed to examine the efficacy of a platinum-based chemotherapy rechallenge after PARP inhibitor therapy. MethodsWe retrospectively evaluated patients with ovarian cancer with a PFI≥6 months with PARP inhibitor maintenance therapy, receiving platinum-based chemotherapy. Duration of PARP inhibitor therapy, best response to subsequent platinum chemotherapy rechallenge, and clinical characteristics were collected from medical records. Tumor response was assessed according to RECIST 1.1. Correlations were calculated using Spearman’s correlation coefficients. ResultsAmong the 10 included patients, seven (70 %) received PARP inhibitors after primary chemotherapy, and three (30 %) received chemotherapy for platinum-sensitive relapse. One and five patients harbored a germline BRCA1 and BRCA wild-type mutations, respectively, and two had homologous recombination proficiency. The median PFI was 303.5 (182–602) days, and PARP inhibitor therapy duration was 249 (147–570) days. Platinum chemotherapy rechallenge efficacy was complete and partial response and stable disease in one (10 %), six (60 %), and three (30 %) patients, respectively. The longer the duration of PARP inhibitor treatment, better the response to platinum agents (Spearman correlation coefficient 0.284, p = 0.0288). ConclusionPlatinum-based chemotherapy rechallenge is reasonable for patients with platinum-sensitive disease, using the traditional PFI cutoff of 6 months, even when the PFI is obtained with a maintenance PARP inhibitor.

Ru(II)-Photoactive Agents for Targeting ER Stress and Immunogenic Cell Death.

Immunotherapy has emerged as a promising avenue for cancer treatment by bolstering the immune system's ability to recognize and attack cancer cells. Photodynamic therapy shows potential in enhancing antitumor immunity, though the mechanisms behind its success are not fully understood. In this manuscript, we investigate two previously reported green light activated PCT/PDT agents where compound 2 - [Ru(tpy)(Me2bpy)( 3 )] 2+ , (tpy = 2,2':6',2''- terpyridine, Me2bpy = 6,6'-dimethyl-2,2'-bipyridine, 3 = pyridyl-BODIPY-I2,) - shows remarkable photoselectivity in assays containing both 2D cancer cells and 3D cocultures containing BALB/c macrophages and 4T1 murine breast cancer cells. Through flow cytometry and protein analysis, we found complex 2 displays superior evidence of induced endoplasmic reticulum (ER) stress markers and indicators of immunogenic cell death (ICD) compared to its ligand 3 , despite its weaker photoselectivity. Most importantly, these results were supported by in vivo studies where 2 produced anti-tumor immunity against the 4T1 tumor model in BALB/c mice. Complete tumor elimination was achieved in 2/8 mice, and these mice were both protected against a subsequent contralateral rechallenge and showed increased ex vivo peripheral tumor antigen-specific recall, suggesting memory T cells are induced by 2 . Signatures of M1 macrophage polarization were also evident in tumor tissue from the remaining 6/8 mice treated with 2 compared to untreated tumors. These findings demonstrate Ru(II) complexation plays a critical role in ER targeting which triggers ICD, highlighting the potential of Ru(II) agents as future in situ tumor vaccines.

Abstract PR006: EG-70 (detalimogene voraplasmid), a novel, non-viral intravesical gene therapy for BCG-unresponsive non-muscle-invasive bladder cancer: Preclinical characterization and translation into the clinic

Abstract Background: EG-70 (detalimogene voraplasmid) is a novel, investigational, non-integrating, non-viral gene therapy specifically engineered to elicit local stimulation of anti-tumor immune response in the bladder and to drive durable efficacy in patients with BCG-unresponsive high-risk non-muscle-invasive bladder cancer (NMIBC), while mitigating the risk of systemic toxicities from immune stimulation. Previous preclinical data indicate that intravesical instillation (IVI) of EG-70 results in local expression of transgene products in murine and non-human primate models. Here we describe the latest preclinical data to support the mechanism of action of EG-70 and Phase 1 clinical study results for EG-70 in the treatment of BCG-unresponsive NMIBC. Methods: Preclinical: A murine surrogate formulation of EG-70 (mEG-70) was administered locally to the bladder by IVI in C57BL/6 mice. Efficacy was assessed in a luciferase-expressing MB49 model of orthotopic bladder cancer. Following confirmation of cancer cell implantation by in vivo imaging, mice received two weekly IVIs of mEG-70. Immune profiling was evaluated by assessing protein expression levels and cell compositions (via MSD, flow cytometry, and immunohistochemistry). Immune cell depletion studies were conducted using specific antibodies directed against CD4 or CD8 antigen to assess T-cell contribution to efficacy. Clinical: In a Phase 1/2 study in high-risk BCG-unresponsive NMIBC with carcinoma in situ (CIS) (LEGEND; NCT04752722), EG-70 was assessed in four separate dose groups. Results: Preclinical: In a mouse model of orthotopic bladder cancer, IVI of mEG-70 caused striking remodeling of the tumor microenvironment from an immunosuppressive phenotype to a pro-inflammatory milieu supportive of tumor clearance. This was demonstrated by a significant decrease in myeloid cells and IL-4 cytokine levels, an increase in NK-cells and T-cells, and an increase in pro-inflammatory cytokines in tumor tissue. Accordingly, administration of mEG-70 was associated with marked reduction in tumor burden and significant improvement of survival. The anti-tumor response was largely immune-mediated as demonstrated by the critical role of T-cells, durable clearance of tumors, and protection against subsequent tumorigenic re-challenge, both locally in the bladder as well as distally, after flank implantation. Clinical: Results from the Phase 1 portion of the LEGEND study show that IVI of EG-70 was well-tolerated in patients with high-risk BCG-unresponsive NMIBC with CIS across all dose levels, with an overall complete response rate of 73%. Conclusions: The latest preclinical findings demonstrate that EG-70 has the potential to deliver immunostimulatory payloads locally to the bladder. The mechanism of action described preclinically has been translated into the clinic, in the Phase 1 portion of the LEGEND study in patients with BCG-unresponsive NMIBC with CIS. Citation Format: Marie-Line Goulet, Shauna M Dauphinee, Daniel Veilleux, Kristine S Louis, David Lazure, Sarah Stevenson, Darius Bilimoria, Fazmina Zamzameer, Ximin Chen, Sébastien Sublemontier, Sahar Amirkhani, Carlos Fleet, Richard Bryce, Matthew Bui, Shreyas Joshi, Susan J. Kalota, Anthony Cheung, James Sullivan. EG-70 (detalimogene voraplasmid), a novel, non-viral intravesical gene therapy for BCG-unresponsive non-muscle-invasive bladder cancer: Preclinical characterization and translation into the clinic [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr PR006.

Abstract 2652: NDI-101150 is a potent and highly selective HPK1 inhibitor that both synergizes with and differentiates from anti-PD1 immune checkpoint blockade

Abstract Introduction HPK1 is a member of the MAP4K family of protein serine/threonine kinases that negatively regulates activation signals in multiple immune cells and is an attractive therapeutic target for many cancers. Using structure-based drug design, we developed a highly selective HPK1 inhibitor, NDI-101150, with nanomolar potency and physiochemical properties suitable for once daily oral administration. Methods & Results HPK1 inhibition with NDI-101150 has a differentiated pharmacology profile when compared directly to PD1 blockade. NDI-101150 was able to overcome the immunosuppressive effects of prostaglandin E2, adenosine, and TGF-β on human T cell activation. HPK1 inhibition also directly limited the suppressive capacity of T regulatory cells. In contrast, anti-PD1 treatment was not able to overcome the immunosuppressive activity associated with any of these mechanisms. In vivo, HPK1 inhibition significantly enhanced the production of antigen-specific antibodies in response to immunization with both T-dependent and T-independent antigens, while anti-PD1 treatment had minimal to no effects on antibody production. In the EMT-6 syngeneic model, 7/10 mice receiving NDI-101150 exhibited complete tumor regressions, compared to only 1/10 from an anti-PD1 cohort. Furthermore, NDI-101150 established a robust and durable immune memory response as 100% of treated mice showed complete rejection of tumor growth upon subsequent re-challenge. HPK1 inhibition with NDI-101150 also shows robust synergy with PD1 blockade in vitro and in vivo. Both NDI-101150 and anti-PD1 were able to reinvigorate exhausted human T cells, restoring cytokine production and proliferative effects in mixed lymphocyte reactions. Further, in combination HPK1 inhibition and PD1 blockade synergized to enhance the activity of exhausted human T cells to an extent exceeding that observed with naïve human T cells in similar experiments. In vivo, while NDI-101150 or anti-PD1 treatments alone induced tumor growth inhibition in the murine CT-26 syngeneic tumor model, NDI-101150 and anti-PD1 in combination mediated complete tumor regressions in several mice. Furthermore, NDI-101150 seemed to induce a durable immune memory response as evidenced by the combination-treated animals showing complete rejection of tumor growth upon subsequent re-challenge, without any further dosing of NDI-101150. Conclusions Pharmacological inhibition of HPK1 with NDI-101150 represents a powerful system-wide immunomodulatory approach with the potential to enhance anti-tumor immunity in patients failing to respond to currently approved immune checkpoint therapies or in combination with immune checkpoint blockade therapies. NDI-101150 is currently being tested in a Phase 1/2 trial (NCT05128487) in patients with advanced solid tumors. Citation Format: David Ciccone, Fu-Shan Kuo, Scott Daigle, Neelu Kaila, Gene Yau, Mark Carlson, Denise Levasseur, Bhaskar Srivastava, Frank G. Basile, Christine Loh. NDI-101150 is a potent and highly selective HPK1 inhibitor that both synergizes with and differentiates from anti-PD1 immune checkpoint blockade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2652.

Abstract 6766: Assessing the impact of immunotherapies and cell therapies in 3D heterospheroid models mimicking tumor microenvironments

Abstract Immunotherapies and cell therapies show substantial potential in the treatment of cancer. However, their efficacy within the complex microenvironment of solid tumors remains a critical area of investigation. In this study, we employ physiologically relevant 3D multicellular heterospheroid models to quantitatively assess the impact of these therapies on immune and tumor cells residing in tumor-like microenvironments. The spheroids are composed of cancer cell lines, fibroblasts and various primary immune cell types matched to the specific target of immunotherapy. We have previously reported that interactions between cancer cells and fibroblasts promote a tumor-like environment, recruiting and polarizing monocytes into M2 macrophages. Treatment of spheroids with immunomodulating compounds successfully reprogrammed the macrophages into M1-like macrophages with increased pro-inflammatory cytokine secretion. To mimic tumor-specific T cell responses observed in cancer patients, we here educated T cells to recognize target cell antigens through a 14-day co-culture of PBMCs and PANC-1 tumor cells. Subsequent re-challenge with PANC-1 heterospheroids revealed 70% specific killing by educated T cells, whereas T cells educated with a breast cancer cell line did not exhibit this targeted cytotoxicity. FACS analysis demonstrated increased expression of activation markers and immune checkpoint molecules such as PD-1, LAG-3 and TIGIT on educated T cells. Furthermore, we observed infiltration of educated CD4+ and CD8+ T cells into heterospheroids by immunohistochemistry, indicating the replication of a tumor-specific response within solid tumors. We are currently investigating the enhancement of educated T cell killing using various immune checkpoint inhibitors including antibodies targeting PD-1, TIGIT and LAG-3. Another means of eliciting tumor-specific responses is by employing CAR T cells. Antigen-specific CAR-T cells or untransduced CAR-T cells derived from the same donor were added to HT-29 and HCT-116 heterospheroids at various target-to-effector ratios. By using cancer cells genetically engineered to express a luciferase enzyme, we assessed the specific killing of cancer cells within the heterospheroids. Analysis showed a clear dose-dependent increase in luminescence, indicating greater antigen-specific CAR-T cell killing potential (60-80% specific lysis) compared to the non-specific killing observed with untransduced CAR-T cells (<5% specific lysis). Additionally, preliminary data demonstrate the killing of heterospheroids by γδ T cells and that this killing is enhanced by immune checkpoint inhibitors. In conclusion, we have developed 3D heterospheroids from various cancer types that faithfully mimic tumor-like microenvironments, enabling us to evaluate the effects of immunotherapies and cell therapies in physiologically relevant models. Citation Format: Natasha Helleberg Madsen, Boye Schnack Nielsen, Kim Holmstrøm, Gitte Olofsson, Per thor Straten, Søren Skov, Carlos Rodriguez-Pardo, Maria Ormhøj, Jesper Larsen, Monika Gad. Assessing the impact of immunotherapies and cell therapies in 3D heterospheroid models mimicking tumor microenvironments [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6766.

Abstract 4189: BALB/c-hIL12RB1/hIL12RB2: A robust model for preclinical research in human IL-12 therapy

Abstract Interleukin-12 (IL-12) is a multifaceted cytokine primarily produced by antigen-activated dendritic cells, macrophages, and neutrophils. Its receptor is a composite of IL12RB1 and IL12RB2, and the union of these two subunits forms a high-affinity receptor complex proficient in mediating IL-12 signaling. As a pivotal regulator of innate and adaptive immunity, IL-12 plays a crucial role in steering the differentiation of naïve T cells into Th1 cells. It is renowned as a T cell stimulatory factor, fostering T cell proliferation. Furthermore, IL-12 has the capacity to augment the activation of cytotoxic lymphocytes and natural killer cells (NK), thereby enhancing interferon (IFN-γ) production. Empirical evidence consistently demonstrates that IL-12 synergistically exerts anti-tumor effects in conjunction with various immune cells, such as T cells and NK cells. Its effectiveness in preclinical studies has solidified IL-12 as an appealing drug target, leading to the development of activating antibodies, therapeutic IL-12 proteins, and tumor vaccines as potential treatments. To delve deeper into the functionality and therapeutic potential of IL-12, we have engineered a humanized mouse model, known as BALB/c-hIL12RB1/hIL12RB2. Notably, this model fully preserves the intracellular domains of mouse IL12RB1 and IL12RB2 proteins, ensuring the normal propagation of intracellular signaling. It also effectively expresses human IL12RB1 and IL12RB2. In vitro functional validation experiments have verified that BALB/c-hIL12RB1/hIL12RB2 mice can proficiently generate IFN-γ when induced by human IL-12. Furthermore, in vivo efficacy experiments have yielded compelling results. Intratumoral administration of human IL-12 mRNA in BALB/c-hIL12RB1/hIL12RB2 mice led to a significant suppression in the growth of CT26 tumors, culminating in complete tumor regression. Subsequent rechallenge experiments conducted after the discontinuation of treatment revealed no tumor recurrence, signifying the enduring inhibitory effect of hIL12 mRNA on mouse tumors. In conclusion, the development of BALB/c-hIL12RB1/hIL12RB2 mice stands as a robust model for advancing preclinical research in the realm of human IL-12 therapy. Citation Format: Yuan Fang, Huiyi Wang, Jun Xing, Lu Yang, Jing Zhao, Xiang Gao, Cunxiang Ju. BALB/c-hIL12RB1/hIL12RB2: A robust model for preclinical research in human IL-12 therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4189.

Efficacy and safety analysis of immune checkpoint inhibitor rechallenge therapy in locally advanced and advanced non-small cell lung cancer: a retrospective study.

Immune checkpoint inhibitors (ICIs) have dramatically changed the first-line treatment pattern of non-small cell lung cancer (NSCLC) without driver gene alterations. However, the optimal choice for second-line treatment after initial treatment with ICIs is unclear. This study aimed to clarify the efficacy and safety of ICI rechallenge therapy in locally advanced and advanced NSCLC. We retrospectively analyzed the histories of 224 patients with locally advanced or advanced NSCLC treated with programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) inhibitors alone or in combination with chemotherapy and/or antiangiogenic therapy in first-line treatment. Progression-free survival 2 (PFS2) was the time from the first defined progress disease (PD) to the second disease progression or death. Efficacy evaluation was performed directly in accordance with RECIST v1.1 criteria. Adverse events (AEs) were graded following the National Cancer Institute Common Terminology Criteria for Adverse Events v5.0. Survival data were estimated using the Kaplan-Meier method or Cox survival regression model and compared using the log-rank test in overall cohort and other subgroups. There were no significant differences in objective response rate (ORR) and median PFS2 (mPFS2) between the ICI rechallenge group and non-rechallenge group (ORR: 10.3% vs. 15.3%, P=0.308; mPFS2: 5.33 vs. 4.40 months, P=0.715). And the ICI rechallenge group showed no new safety signals compared with non-rechallenge group. In ICI rechallenge group, patients resistant to first-line immunotherapy had a lower ORR and shorter PFS2 compared with those who responded to initial ICIs treatment (ORR: 7.0% vs. 17.6%, P=0.038; mPFS2: 3.68 vs. 5.91 months, P=0.014). No significant difference in mPFS2 was observed among different second-line treatment groups (P=0.362). Radiotherapy in second-line treatment and ICI rechallenge therapy were not the main factors affecting PFS2. ICI rechallenge therapy beyond disease progression did not improve clinical outcomes in patients with NSCLC, but no new safety signals emerged. However, patients with favorable response to initial ICIs treatment still showed significant efficacy of subsequent ICI rechallenge therapy.

Inhalable extracellular vesicle delivery of IL-12 mRNA to treat lung cancer and promote systemic immunity.

Lung carcinoma is one of the most common cancers and has one of the lowest survival rates in the world. Cytokines such as interleukin-12 (IL-12) have demonstrated considerable potential as robust tumour suppressors. However, their applications are limited due to off-target toxicity. Here we report on a strategy involving the inhalation of IL-12 messenger RNA, encapsulated within extracellular vesicles. Inhalation and preferential uptake by cancer cells results in targeted delivery and fewer systemic side effects. The IL-12 messenger RNA generates interferon-γ production in both innate and adaptive immune-cell populations. This activation consequently incites an intense activation state in the tumour microenvironment and augments its immunogenicity. The increased immune response results in the expansion of tumour cytotoxic immune effector cells, the formation of immune memory, improved antigen presentation and tumour-specific T cell priming. The strategy is demonstrated against primary neoplastic lesions and provides profound protection against subsequent tumour rechallenge. This shows the potential for locally delivered cytokine-based immunotherapies to address orthotopic and metastatic lung tumours.

Abstract B141: Evaluation of antigen-agnostic anti-tumor activity and immunological memory induced by CBX-15 (alphalexTM-MMAE) in the rat syngeneic breast cancer model

Abstract CBX-15 is a peptide-drug conjugate consisting of alphalexTM-monomethyl auristatin E (MMAE). The alphalexTM is a unique variant of pH-Low Insertion Peptide1 (pHLIP®) designed to target the low pH microenvironment of cancer cells, a universal feature of all rapidly growing tumors. The peptide of CBX-15 forms an alpha helix only in low pH conditions, resulting in unidirectional insertion of the peptide and delivery of MMAE across the cancer cell membrane, and avoidance of delivery to healthy tissues, including immune cells. Efficacy and anti-tumor immunological memory induced by CBX-15 was evaluated in Fischer 344 rats bearing syngeneic 13762 mammary adenocarcinoma tumors. The development of anti-tumor immunological memory was examined in CBX-15-cured animals by in vivo/ex vivo rechallenge with live tumor cells and subsequent assessment of tumor rejection, cytokine release by T cells, tumor immune cell infiltration, and memory T cell composition of the bone marrow. CBX-15 rapidly regressed rat tumors, resulting in complete responses while sparing healthy tissues such as bone marrow. Cured rats rejected live tumor rechallenge and exhibited a doubling of bone marrow-resident CD4 memory T cells 50 days post-dose. Splenocytes and lymph node suspensions derived from cured rats demonstrated formation of a Th1-mediated IFNƳ response when exposed ex vivo to tumor cells. The ability of CBX-15 to induce immunogenic cell death was established by vaccinating syngeneic animals with CBX-15 treated tumor cells and subsequent tumor rechallenge, which demonstrated anti-tumor immunity induced by CBX-15. These preclinical data demonstrate the anti-tumor efficacy of CBX-15 in the rat as well as the ability of CBX-15 to enhance tumor immunogenicity through immunogenic cell death by utilizing a universal pH-based tumor targeting mechanism.1 Wyatt LC et al. 2017. Applications of pHLIP Technology for Cancer Imaging and Therapy. Trends Biotech. Citation Format: Sophia Gayle, Timothy Paradis, Qing Zhang, Laurie Tylaska, Connor Hagen, Theresa Pasqualini, Vishwas Paralkar. Evaluation of antigen-agnostic anti-tumor activity and immunological memory induced by CBX-15 (alphalexTM-MMAE) in the rat syngeneic breast cancer model [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B141.

CTIM-22. PHASE I STUDY RESULTS OF THE ANTIBODY-CYTOKINE FUSION PROTEIN L19TNF IN COMBINATION WITH LOMUSTINE FOR PATIENTS WITH RECURRENT GLIOBLASTOMA REVEAL PROMISING SAFETY AND DURABLE TUMOR RESPONSES

Abstract Treatment options for recurrent glioblastoma are limited and there is a need for novel effective therapies. Recently, we showed synergistic preclinical anti-tumor activity of the immunocytokine L19TNF in combination with lomustine in orthotopic immunocompetent glioma mouse models. L19TNF is an antibody-cytokine fusion protein, comprising the pro-inflammatory cytokine tumor necrosis factor (TNF) fused to the antibody L19 that binds to a tumor-specific epitope of the extracellular matrix protein fibronectin. This allows a targeted delivery of therapeutically relevant doses of TNF to the tumor site through intravenous administration while sparing healthy tissues. Here, we present results of the completed phase I part of a phase I/II open label, multicenter, randomized study to investigate L19TNF in combination with lomustine for patients with recurrent glioblastoma (NCT04573192). Fifteen patients were enrolled from February 2021 – January 2023 and treated at three different dose levels of L19TNF in combination with lomustine. Overall, the treatment was well tolerated. The most common adverse events were asymptomatic increase of liver function tests and a decrease of white blood cells and platelets. Serial MRI assessments revealed near-complete responses in 3 patients (20%) and stable disease in 8 (53%) patients. The median progression-free survival was 4.2 months, progression-free survival rate at 6 months was 46% (7/15 patients), and median overall survival has not been reached after a median follow-up of 11 months. Serial blood assessments demonstrated a treatment-associated increase in C-reactive protein, a peripheral marker for inflammation, which correlated with progression-free survival. A patient, who showed a near-complete response that lasted 12 months relapsed at a different location. Subsequent re-challenge with L19TNF and lomustine again led to a partial response. These encouraging results justify further investigations within the phase II part of the clinical trial that is recruiting patients in four countries.

EXTH-24. FC-ENHANCED ANTI-CTLA-4 IMMUNE CHECKPOINT BLOCKADE AND ITS COMBINATION WITH ANTI-PD-1 WITH CONCOMITANT DOXORUBICIN AND ULTRASOUND-MEDIATED BBB OPENING: A NOVEL IMMUNOTHERAPY FOR GLIOBLASTOMA

Abstract Despite the recent success of immune checkpoint blockade in various cancer types, glioblastoma (GBM) remains resistant to immunotherapy due to its immunosuppressive features and the poor penetration of systemic agents across the blood-brain barrier (BBB). Recent clinical trials demonstrated the unprecedented efficacy of Fc enhanced anti-CTLA-4, an anti-CTLA-4 antibody with enhanced affinity to Fcγ receptors (FcE-aCTLA-4), against immunologically inactive (‘cold’) tumors. This agent exhibits a high affinity for FcγRIIIA regardless of its polymorphic variants of FcgRIIIA that are known to influence the binding affinity and efficacy of conventional anti-CTLA-4 antibodies. We observed robust expression of FcγRIIIA in tumor-associated macrophages/myeloid cells (TAM) of human GBM, which was most pronounced in newly diagnosed GBM. FcE-aCTLA-4 demonstrated high-affinity binding to FcγRIV, the mouse ortholog of human FcγRIIIA, which was highly expressed on TAMs in mouse gliomas. We evaluated the efficacy of the murine homologous FcE-aCTLA-4 antibody as monotherapy and in combination with other treatments in several murine glioma models. FcE-aCTLA-4 selectively depleted CTLA-4 expressing intra-tumoral regulatory T cells (Tregs) via antibody-dependent phagocytosis by TAMs while spearing peripheral Tregs and other CD4+ T cell populations. In a cohort of 4 GBM patients, doxorubicin delivered with low-intensity pulsed ultrasound and microbubbles (LIPU/MB), a procedure that temporarily opens the BBB, upregulated FcγRIIIA expression on TAMs. Treatment of immunotherapy-resistant murine gliomas with a combination of FcE-aCTLA-4, anti-PD-1, and doxorubicin with concomitant LIPU/MB resulted in over 90% cure rates, which correlated with increased infiltration of activated CD8+ T cells in the brain, and complete rejection upon subsequent tumor rechallenge. Our findings indicate that FcE-aCTLA-4 exhibits a novel immunomodulatory function in GBM, and its therapeutic potential is significantly improved when combined with anti-PD-1, doxorubicin, and delivered by LIPU/MB. This therapy warrants further evaluation in clinical trials.

Intraperitoneal administration of a modified vaccinia virus Ankara confers single-chain interleukin-12 expression to the omentum and achieves immune-mediated efficacy against peritoneal carcinomatosis

BackgroundPeritoneal carcinomatosis is an advanced stage of cancer in which the disease has spread to the peritoneal cavity. In order to restore antitumor immunity subverted by tumor cells in this...

Humoral and cellular responses to repeated COVID-19 exposure in multiple sclerosis patients receiving B-cell depleting therapies: a single-center, one-year, prospective study.

Multiple sclerosis patients treated with anti-CD20 therapy (aCD20-MS) are considered especially vulnerable to complications from SARS-CoV-2 infection due to severe B-cell depletion with limited viral antigen-specific immunoglobulin production. Therefore, multiple vaccine doses as part of the primary vaccination series and booster updates have been recommended for this group of immunocompromised individuals. Even though much less studied than antibody-mediated humoral responses, T-cell responses play an important role against CoV-2 infection and are induced efficiently in vaccinated aCD20-MS patients. For individuals with such decoupled adaptive immunity, an understanding of the contribution of T-cell mediated immunity is essential to better assess protection against CoV-2 infection. Here, we present results from a prospective, single-center study for the assessment of humoral and cellular immune responses induced in aCD20-MS patients (203 donors/350 samples) compared to a healthy control group (43/146) after initial exposure to CoV-2 spike antigen and subsequent re-challenges. Low rates of seroconversion and RBD-hACE2 blocking activity were observed in aCD20-MS patients, even after multiple exposures (responders after 1st exposure = 17.5%; 2nd exposure = 29.3%). Regarding cellular immunity, an increase in the number of spike-specific monofunctional IFNγ+-, IL-2+-, and polyfunctional IFNγ+/IL-2+-secreting T-cells after 2nd exposure was found most noticeably in healthy controls. Nevertheless, a persistently higher T-cell response was detected in aCD20-MS patients compared to control individuals before and after re-exposure (mean fold increase in spike-specific IFNγ+-, IL-2+-, and IFNγ+/IL-2+-T cells before re-exposure = 3.9X, 3.6X, 3.5X/P< 0.001; after = 3.2X, 1.4X, 2.2X/P = 0.002, P = 0.05, P = 0.004). Moreover, cellular responses against sublineage BA.2 of the currently circulating omicron variant were maintained, to a similar degree, in both groups (15-30% T-cell response drop compared to ancestral). Overall, these results highlight the potential for a severely impaired humoral response in aCD20-MS patients even after multiple exposures, while still generating a strong T-cell response. Evaluating both humoral and cellular responses in vaccinated or infected MS patients on B-cell depletion therapy is essential to better assess individual correlations of immune protection and has implications for the design of future vaccines and healthcare strategies.

Development of a novel modified vaccine (TheraVacM) for curative treatment of mouse solid tumors

Monotherapy with immune checkpoint blockade (ICB) antibodies (anti-CTLA4 and anti-PD1/PDL-1) is only effective for 20% to 30% of patients with certain cancers. Patients with cancers harboring few effector T cells (Teffs) are insensitive to ICB therapy. The lack of tumor-specific Teffs is predominantly caused by the paralysis of tumor-infiltrating dendritic cells (TiDCs) resulting from immunosuppression in the tumor microenvironment. We have identified a potent combination of high mobility group nucleosome binding domain 1 (HMGN1, N1) and fibroblast stimulating lipopeptide-1 (FSL-1) that can synergistically trigger maturation of both mouse and human DCs. Accordingly, we designed a combinational anti-cancer immunotherapy with two arms: an immune-activating arm consisting of N1 and FSL-1 to stimulate the generation of Teffs by triggering full maturation of TiDCs, and an ICB arm using anti-PDL-1 or anti-CTLA4 to prevent Teffs from being silenced in the tumor tissue. This combinational immunotherapeutic vaccination regimen dubbed modified TheraVac (TheraVacM) has proved particularly effective as it cured 100% of mice bearing established ectopic CT26 colon and RENCA kidney tumors. The resultant tumor-free mice were resistant to subsequent re-challenge with the same tumors, indicating the generation of long-term tumor specific protective immunity. Since the immune-activating arm also induces full maturation of human DCs, and anti-PDL-1 or anti-CTLA4 have been FDA-approved, this combinational immunotherapy has the potential to be an effective clinical therapy for patients with solid tumors.

Abstract 5745: Proposing the best MET inhibitor to improve anti-PD-1 efficacy in HCC

Abstract Despite recently approved immunotherapy combinations, Hepatocellular carcinoma (HCC) remains among the most therapeutically intractable cancers with a 5-year survival rate of only 18%. Underlying chronic liver disease due to hepatitis B/C infection, alcohol abuse, hemochromatosis, or nonalcoholic steatohepatitis promotes HCC development. Current therapeutic strategies include surgery, radiotherapy and multikinase inhibitors alone or with immune-checkpoint blockade (ICB). In particular, the receptor tyrosine kinase MET and its ligand hepatocyte growth factor (HGF) are known drivers of HCC through promotion of tumor growth, survival, tissue invasion, and angiogenesis. Previously, our collaborators showed that the limited clinical benefit of MET kinase inhibition was partially a result of induced upregulation PD-L1 leading to local T cell suppression. We hypothesized that combining MET inhibition with blockade of the PD-1 immune checkpoint would overcome the limitations of each individual approach and act synergistically to promote HCC tumor regression. We first validated that both MET selective (Capmatinib and Tivantinib) and non-selective (Cabozantinib) inhibitors all induced PD-L1 on HCC cell lines in vitro. Next, we compared Capmatinib and Cabozantinib alone and with PD-1 ICB in vivo in the ICB-sensitive Hepa1-6 and HCA-1 models of HCC. In HCA-1, statistically significant benefit of the MET inhibitor and αPD-1 combination was evident in limitation of tumor growth and extension of survival. In each case, the Capmatinib combination trended toward better outcomes with PD-1 blockade. Mechanistically, the Capmatinib and αPD-1 combination decreased tumor Treg cells while promoting increased accumulation of activated, non-exhausted, proliferating CD8 T cells. Central memory CD8 T cell frequencies were increased by the combination during the effector phase, and combination treated animals were better protected against subsequent rechallenge than those cured by αPD-1 alone. In the myeloid compartment, M1 macrophage frequencies were increased while PMN-MDSC both decreased in frequency and in Arginase 1 levels. Finally, we studied a serially-passaged, αPD-1 refractory DEN HCC model. Despite lack of efficacy of either component therapy, the MET inhibitor and αPD-1 combination significantly extended survival and inhibited tumor growth. As in the αPD-1 sensitive setting, Capmatinib appeared to offer the most therapeutic benefit with αPD-1. Ongoing studies are focused on characterizing changes mediated by the combination therapy which confer aPD-1 sensitivity to the otherwise refractory DEN HCC tumor microenvironment. Molecular studies are focused on understanding the superior ICB potentiating capacity of Type I MET inhibitors versus the other classes. Given the clinical availability of numerous MET and PDL-1 inhibitors, we hope to inform near-term optimization of MET and αPD-1 clinical trial design for HCC. Citation Format: Ricardo A. de Azevedo, Broderick Turner, Priyamvada Jayaprakash, Krithikaa Rajkumar Bhanu, Anupallavi Srinivasamani, Brittany Morrow, Michelle Winkler, Shweta Mahendra Hedge, Arthur Liu, Ravaen Slay, Michael A. Curran. Proposing the best MET inhibitor to improve anti-PD-1 efficacy in HCC. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5745.

Abstract 2731: STX-001, a locally administered LNP-formulated self-replicating mRNA that encodes the therapeutic payload IL-12, induces deep systemic immune responses to solid tumors

Abstract Critical advances in immunotherapies have expanded treatment options and improved patient outcomes across many solid tumor indications. However, durable clinical responses conferred by immunotherapies such as immune checkpoint inhibitors are experienced in only a minority of patients, in part because these therapies fail to sufficiently activate and recruit T cells into the tumor. Therapeutic use of cytokines to potently stimulate tumor-reactive T cells have shown great promise in treating solid tumors but a narrow therapeutic index has precluded their development in the clinic. To overcome these limitations, we developed STX-001, a multi-modal synthetic self-replicating mRNA technology that delivers a prolonged and locally-acting IL-12 cytokine to the tumor microenvironment. STX-001, when delivered directly to the tumor, induces a highly immunogenic tumor cell death while the mRNA-encoded IL-12 payload promotes recruitment of effector T cells and NK cells into the tumor microenvironment. The self-replicating nature of STX-001 enables delivery of therapeutic quantities of IL-12 at dose levels that are orders of magnitude lower than conventional mRNA. STX-001 produces IL-12 upon intratumoral delivery to patient-derived xenografts and the IL-12 payload encoded in STX-001 exhibits similar activity to native IL-12. Using a murine surrogate, a single dose of STX-001 induces deep anti-tumor responses, eradicating tumors in multiple murine models, and promoting responses that are durable against subsequent rechallenge. Furthermore, intratumoral delivery of a single dose of STX-001 controls the growth of distal untreated tumors suggesting capability of promoting systemic immune responses or abscopal effects. Lastly, combination of STX-001 with PD-1/PD-L1 axis inhibitors further enhances efficacy in PD-1 refractory preclinical models. Taken together, our preclinical data demonstrates that STX-001 has potential to overcome limitations of current immunotherapy approaches to improve clinical responses to solid tumors. Citation Format: Ryan T. Sowell, Jaspreet S. Khurana, Zhijun Su, Weiyu Zhao, Gautam N. Shenoy, Madhuri Dey, Alexander C. Lemaire, Anna J. Simon, Ashley G. Njiru, Ryan A. Patenaude, Britt A. DiMarzio, Daniel T. Dzurko, Daniel W. Gately, Aidan B. Coia, Wuhbet D. Abraham, Julian Quiñones, Aalok Shah, Joseph L. Barberio, Prashant R. Nambiar, Jacob R. Becraft, Tasuku Kitada. STX-001, a locally administered LNP-formulated self-replicating mRNA that encodes the therapeutic payload IL-12, induces deep systemic immune responses to solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2731.

EXTH-60. ONCR-GBM, A NOVEL ARMED ONCOLYTIC HSV-1 VECTOR ENGINEERED FOR EFFICACY AND SAFETY IN GLIOBLASTOMA

Abstract Glioblastoma (GBM) is the most common type of primary brain tumor in adults, with a 5-year overall survival of only 7%. Oncolytic viruses are a promising and active area of research in GBM with the recent approval of an oncolytic HSV-1 vector, teserpaturev (Delytact, also known as G47Δ, Daiichi Sankyo) for recurrent GBM based on an overall survival of 92% at 1 year. G207, an HSV-1 vector more attenuated than teserpaturev, recently reported acceptable tolerability with evidence of responses in children with recurrent or progressive high-grade glioma. These vectors are not expressing any cDNA transgene that may enhance and prolong antitumor activity. We report here the development of ONCR-GBM, an oncolytic HSV-1 vector specifically engineered for safety using a microRNA attenuation strategy to limit viral replication in healthy cell type of the CNS. ONCR-GBM has been developed from a novel potently oncolytic strain of HSV-1 and optimized for infection of GBM tumor cells. Antitumor efficacy has been further enhanced through the expression of multiple payloads designed to modify the immunosuppressive tumor microenvironment of GBM. We previously reported that a vector expressing IL-12 and a PD-1 antagonist nanobody achieved &amp;gt; 90% survival after a single injection in the GL261-Nectin1 orthotopic model. This vector promoted immune cell recruitment and activation in tumors and protected surviving animals from a subsequent tumor rechallenge. Additional payloads selected for interfering with the immune suppressive stroma in GBM have been evaluated for potentiating the response of IL-12 and anti PD-1 expressing HSV-1. We will present the outcome of the in vivo screen, and the selection of the optimal combination of payloads featured in ONCR-GBM clinical candidate.