Combined CTLA-4 Research Articles

Targeting immunosuppressive Ly6C+ classical monocytes reverses anti-PD-1/CTLA-4 immunotherapy resistance.

Despite significant clinical advancement with the use of immune checkpoint blockade (ICB) in non-small cell lung cancer (NSCLC) there are still a major subset of patients that develop adaptive/acquired resistance. Understanding resistance mechanisms to ICB is critical to developing new therapeutic strategies and improving patient survival. The dynamic nature of the tumor microenvironment and the mutational load driving tumor immunogenicity limit the efficacy to ICB. Recent studies indicate that myeloid cells are drivers of ICB resistance. In this study we sought to understand which immune cells were contributing to resistance and if we could modify them in a way to improve response to ICB therapy. Our results show that combination anti-PD-1/CTLA-4 produces an initial antitumor effect with evidence of an activated immune response. Upon extended treatment with anti-PD-1/CTLA-4 acquired resistance developed with an increase of the immunosuppressive populations, including T-regulatory cells, neutrophils and monocytes. Addition of anti-Ly6C blocking antibody to anti-PD-1/CTLA-4 was capable of completely reversing treatment resistance and restoring CD8 T cell activity in multiple KP lung cancer models and in the autochthonous lung cancer KrasLSL-G12D/p53fl/fl model. We found that there were higher classical Ly6C+ monocytes in anti-PD-1/CTLA-4 combination resistant tumors. B7 blockade illustrated the importance of dendritic cells for treatment efficacy of anti-Ly6C/PD-1/CTLA-4. We further determined that classical Ly6C+ monocytes in anti-PD-1/CTLA-4 resistant tumors are trafficked into the tumor via IFN-γ and the CCL2-CCR2 axis. Mechanistically we found that classical monocytes from ICB resistant tumors were unable to differentiate into antigen presenting cells and instead differentiated into immunosuppressive M2 macrophages or myeloid-derived suppressor cells (MDSC). Classical Ly6C+ monocytes from ICB resistant tumors had a decrease in both Flt3 and PU.1 expression that prevented differentiation into dendritic cells/macrophages. Therapeutically we found that addition of anti-Ly6C to the combination of anti-PD-1/CTLA-4 was capable of complete tumor eradication. Classical Ly6C+ monocytes differentiate into immunosuppressive cells, while blockade of classical monocytes drives dendritic cell differentiation/maturation to reinvigorate the anti-tumor T cell response. These findings support that immunotherapy resistance is associated with infiltrating monocytes and that controlling the differentiation process of monocytes can enhance the therapeutic potential of ICB.

Single-cell RNA and T cell receptor (TCR) sequencing in patients with HPV-positive head and neck squamous cell carcinoma (HNSCC) after induction CTLA4 and PD-1 immune checkpoint blockade (ICB).

6056 Background: Combination CTLA-4 and PD-1 ICB results in durable responses in patients with recurrent and metastatic HNSCC and therefore justifies further investigation in the induction or neoadjuvant setting. Methods: We investigated features of the tumor immune microenvironment (TIME) associated with MHR after induction CTLA-4 and PD-1 ICB in patients with newly diagnosed HPV-positive HNSCC. Tumor samples were collected at baseline and on treatment from 31 patients enrolled in a phase 2 trial of a 6-week cycle of CTLA-4 and PD-1 ICB induction followed by dose/volume-adapted IMRT (50-66Gy) concurrent with cycle 2. Tumors were evaluated for histological response and single-cell RNA sequencing (scRNA-seq) and scTCR-seq were performed on the 10X genomics platform. After stringent clustering and annotation of scRNA-seq data, 76,319 CD8+ and 78,622 CD4+ T cells with paired TCR sequence data were evaluable for transcriptomic, TCR repertoire and clonotype differentiation analysis. Results: Percent reduction in tumor viability on histology correlated significantly with reduction in tumor cell proportion in scRNA-seq data (R2= 0.7). Thirteen (48%) of 27 patients with paired samples (missing data due to COVID) had MHR, defined as ≤10% residual tumor viability on ICB treatment. Through TCR tracing, over 100 T cell clonotypes that expanded significantly (p < 0.05, Fisher’s exact) post-ICB were identified. Highly expanded clonotypes resided mainly in exhausted CD8+ T cell clusters and exhibited a tissue resident memory (TRM) phenotype. Examination of their functional states revealed a variety of T cell modulatory trajectories, including reverse transition from exhausted to less exhausted states and from memory to functional states. When compared to patients without MHR, those with MHR had significantly higher ICB-induced TCR clonotype expansion (p = 0.025, Wilcoxon), reductions of activated Tregs (p = 0.003, Wilcoxon) and terminally exhausted CD8+ T cells (p = 0.003, Wilcoxon), and increase of polyfunctional CD8+ T cells (p = 0.014, Wilcoxon). A lasso regression model associated T cell expansion, basal 7-gene TRM and 5-gene effector scores, and on-treatment proliferation score and effector cell proportion with percent reduction in tumor viability (R2 = 0.66). Conclusions: In HPV-HNSCC, induction CTLA4 and PD1 ICB lead to extensive reinvigoration of CD8+ T cell clonotypes with both an exhausted and TRM phenotype, revealing a high degree of plasticity of distinct T cell clones. Paired RNA and TCR profiling facilitated identification of potentially tumor reactive and ICB-responsive T cells and clonotypes and identified several TIME features associated with tumor cell death. Clinical trial information: NCT03799445 .

Updated results from an ongoing phase 1/2a study of T3011, an oncolytic HSV expressing IL-12 and PD-1 antibody, administered via IT injection as monotherapy or combined with pembrolizumab in advanced solid tumors.

9535 Background: T3011 is a recombinant HSV-1 oncolytic virus expressing both IL-12 and anti-human PD-1 antibody. Upon injection, locally produced IL-12 induces IFN-γ production, enhances the oncolytic activity of NK cells and cytotoxic T lymphocytes, promotes anti-angiogenesis and inhibits tumor growth. PD-1 antibodies act as immune checkpoint inhibitors to augment tumor-killing activity of T-cells. Here we report the updated results from an open-label, dose escalation and expansion study of T3011 administered via intratumoral injection as monotherapy or in combination with intravenous pembrolizumab. Methods: Pts with pathologically confirmed recurrent or metastatic malignancy after failure of SOC were enrolled and received T3011 monotherapy (1*106-5*107 PFU/mL Q2W) or in combination with pembrolizumab (Lead-in T3011 1*106 PFU/mL Q2W monotherapy for 2 cycles followed by combination therapy Q3W). Pts with documented progression on T3011 monotherapy may cross over to receive combination therapy at the discretion of the investigator. The primary endpoints were safety and tolerability. Key secondary endpoints included confirmed ORR, DCR, DOR, PFS by investigator per RECIST1.1; OS; PD and PK. Results: As of 17 Jan 2023, 29 pts received T3011 alone or in combination with pembrolizumab, the median follow-up was 14.1 (1.2-27.6) months. No DLTs were reported. Any treatment-related adverse events (TRAEs) occurred in 75.9% (22/29) of pts (≥G3 in 10.3%). Treatment-related SAEs occurred in 3.4% (1/29). Most frequent TRAEs (≥10%) were pyrexia (27.6%), fatigue (20.7%) and chills, injection site pain, arthralgia, nausea, headache (10.3% each). No additional safety signals were observed with combination therapy. 12 advanced melanoma pts failing prior PD-1 or PD-1/CTLA-4 combination treatment received 5*107 PFU/mL of T3011 monotherapy. The confirmed ORR and DCR were 25.0% (3/12) and 33.3% (4/12), respectively. 12-month PFS rate was 36.4%. 6 of these pts were re-challenged with immunotherapy with T3011 (5*107 PFU/mL) combined with pembrolizumab after progressing on T3011 monotherapy, 1 pt achieved PR after 4 months lasting > 8 months at data cutoff. 15 pts had tumor tissues for PD analysis. Increased CD8+ cells were observed in 46.7% (7/15) of all pts and 50% (5/10) of melanoma pts. It appeared to be more pronounced in pts with PR and SD, 66.7% (6/9) in all pts and 80% (4/5) in melanoma pts, respectively. Notably, the increment of CT8+ cells in 2 melanoma pts with PR was over 15 folds. Conclusions: Both T3011 IT monotherapy and combination therapy with pembrolizumab were safe and tolerable. The efficacy of T3011 in immune-resistant melanoma was encouraging. Our data suggest T3011 may modify the tumor microenvironment and overcome immune resistance. Clinical trial information: NCT04370587 .

Brief Report: Safety and Antitumor Activity of Durvalumab Plus Tremelimumab in Programmed Cell Death-(Ligand)1–Monotherapy Pretreated, Advanced NSCLC: Results From a Phase 1b Clinical Trial

IntroductionAlthough first-line immunotherapy approaches are standard, in patients with non-small cell lung cancer (NSCLC) previously treated with programmed cell death protein-1 or programmed death-(ligand)1 (PD-[L]1) inhibitors, the activity of combined CTLA-4 plus PD-(L)1 inhibition is unknown. This phase 1b study evaluated the safety and efficacy of durvalumab plus tremelimumab in adults with advanced NSCLC who received anti–PD-(L)1 monotherapy as their most recent line of therapy. MethodsPatients with PD-(L)1–relapsed or refractory NSCLC were enrolled between October 25, 2013, and September 17, 2019. Durvalumab 20 mg/kg plus tremelimumab 1 mg/kg was administered intravenously every 4 weeks for four doses, followed by up to nine doses of durvalumab monotherapy every 4 weeks for up to 12 months of treatment or disease progression. Primary end points included safety and objective response rate (ORR) on the basis of Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1) per blinded independent central review; secondary end points were ORR on the basis of RECIST v1.1 per investigator; duration of response, disease control, and progression-free survival on the basis of RECIST v1.1 per blinded independent central review and investigator; and overall survival. ClinicalTrials.gov identifier: NCT02000947. ResultsPD-(L)1–refractory (n = 38) and PD-(L)1–relapsed (n = 40) patients were treated. The most common treatment-related adverse events were fatigue (26.3%, PD-(L)1–refractory patients) and diarrhea (27.5%, PD-(L)1–relapsed patients). Grade 3 to 4 treatment-related adverse events occurred in 22 patients. Median follow-up duration was 43.6 months for PD-(L)1–refractory patients and 41.2 months for PD-(L)1–relapsed patients. The ORR was 5.3% for PD-(L)1–refractory patients (one complete response, one partial response) and 0% for PD-(L)1–relapsed patients. ConclusionsDurvalumab plus tremelimumab had a manageable safety profile, but the combination did not have efficacy after PD-(L)1 treatment failure.

A Mathematical Model for Predicting Patient Responses to Combined Radiotherapy with CTLA-4 Immune Checkpoint Inhibitors.

The purpose of this study was to develop a cell-cell interaction model that could predict a tumor's response to radiotherapy (RT) combined with CTLA-4 immune checkpoint inhibition (ICI) in patients with hepatocellular carcinoma (HCC). The previously developed model was extended by adding a new term representing tremelimumab, an inhibitor of CTLA-4. The distribution of the new immune activation term was derived from the results of a clinical trial for tremelimumab monotherapy (NCT01008358). The proposed model successfully reproduced longitudinal tumor diameter changes in HCC patients treated with tremelimumab (complete response = 0%, partial response = 17.6%, stable disease = 58.8%, and progressive disease = 23.6%). For the non-irradiated tumor control group, adding ICI to RT increased the clinical benefit rate from 8% to 32%. The simulation predicts that it is beneficial to start CTLA-4 blockade before RT in terms of treatment sequences. We developed a mathematical model that can predict the response of patients to the combined CTLA-4 blockade with radiation therapy. We anticipate that the developed model will be helpful for designing clinical trials with the ultimate aim of maximizing the efficacy of ICI-RT combination therapy.

Safety and clinical efficacy of immune checkpoint inhibition and stereotactic body radiotherapy in patients with spine metastasis.

Immunotherapy, particularly immune checkpoint inhibitors (ICIs), has revolutionized the treatment of patients with many tumor histologies. Simultaneously, stereotactic body radiotherapy (SBRT) provides excellent local control (LC) and plays an important role in the management of spine metastasis. Promising preclinical work suggests the potential therapeutic benefit of combining SBRT with ICI therapy, but the safety profile of combined therapy is unclear. This study aimed to evaluate the toxicity profile associated with ICI in patients receiving SBRT and, secondarily, whether ICI administration sequence with respect to SBRT affects LC or overall survival (OS) outcomes. The authors retrospectively reviewed patients with spine metastasis treated with SBRT at an academic center. Patients who received ICI at any point during their disease course were compared to those with the same primary tumor types who did not receive ICI by using Cox proportional hazards analyses. Primary outcomes were long-term sequelae, including radiation-induced spinal cord myelopathy, esophageal stricture, and bowel obstruction. Secondarily, models were created to evaluate OS and LC in the cohort. Two hundred forty patients who received SBRT to 299 spine metastases were included in this study. The most common primary tumor types were non-small cell lung cancer (n = 59 [24.6%]) and renal cell carcinoma (n = 55 [22.9%]). One hundred eight patients received at least 1 dose of ICI, with the most common regimen being single-agent anti-PD-1 (n = 80 [74.1%]), followed by combination CTLA-4/PD-1 inhibitors (n = 19 [17.6%]). Three patients experienced long-term radiation-induced sequelae: 2 had esophageal stricture and 1 had bowel obstruction. No patients developed radiation-induced myelopathy. There was no association between receipt of ICI and development of any of these adverse events (p > 0.9). Similarly, ICI was not significantly associated with either LC (p = 0.3) or OS (p = 0.6). In the entire cohort, patients who received ICI prior to beginning SBRT had worse median survival, but ICI sequence with respect to SBRT was not significantly prognostic of either LC (p > 0.3) or OS (p > 0.07); instead, baseline performance status was most predictive of OS (HR 1.38, 95% CI 1.07-1.78, p = 0.012). Treatment regimens that combine ICIs before, concurrent with, and after SBRT for spine metastases are safe, with minimal risk for increased rates of long-term toxicity.

CO-induced TTP improves efficacy through resetting tumor-associated macrophages toward M1 phenotype in combined CTLA-4 and PD-1 blockade immunotherapy

Abstract Combined immune checkpoint blockade (CICB) targeting CTLA-4 and PD-1 has improved the prognosis for many malignancies, but also occurred a high rate of immune-related adverse events (irAEs). The manifestation of these toxicities is an important limiting factor for the successful implementation of CICB, restraining its anti-tumor efficacy. Carbon monoxide (CO), a pivotal endogenous signaling molecule, is able to maintain cell and tissue homeostasis and could be used as a therapeutic regimen. In our previous reports, CO could be useful therapeutics for the regulation of various inflammatory diseases through the increase of tristetraprolin (TTP) that binds to the AU-rich elements in target mRNA. In this study, we observed that CO-induced TTP activation ameliorated colitis and hepatitis, and improved anti-tumor efficacy in CICB treatment. We found that the colitis and hepatitis in TTP deficient mice were further exacerbated by CICB treatment. Moreover, CO increases CICB efficacy through TAM to M1 polarization together with diminishes irAEs through TTP enhancement in several irAEs target organ. Thus, we suggest that CO might be efficiently decouples anti-tumor efficacy and toxicity of CICB through TTP enhancement.

Combination of CTLA-4 and PD-1/PD-L1 Immune Checkpoints Inhibitors for Treatment of Cancer

Combination of CTLA-4 and PD-1/PD-L1 Immune Checkpoints Inhibitors for Treatment of Cancer

Driver Mutations Dictate the Immunologic Landscape and Response to Checkpoint Immunotherapy of Glioblastoma.

The composition of the tumor immune microenvironment (TIME) is considered a key determinant of patients' response to immunotherapy. The mechanisms underlying TIME formation and development over time are poorly understood. Glioblastoma (GBM) is a lethal primary brain cancer for which there are no curative treatments. GBMs are immunologically heterogeneous and impervious to checkpoint blockade immunotherapies. Utilizing clinically relevant genetic mouse models of GBM, we identified distinct immune landscapes associated with expression of EGFR wild-type and mutant EGFRvIII cancer driver mutations. Over time, accumulation of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) was more pronounced in EGFRvIII-driven GBMs and was correlated with resistance to PD-1 and CTLA-4 combination checkpoint blockade immunotherapy. We determined that GBM-secreted CXCL1/2/3 and PMN-MDSC-expressed CXCR2 formed an axis regulating output of PMN-MDSCs from the bone marrow leading to systemic increase in these cells in the spleen and GBM tumor-draining lymph nodes. Pharmacologic targeting of this axis induced a systemic decrease in the numbers of PMN-MDSC, facilitated responses to PD-1 and CTLA-4 combination checkpoint blocking immunotherapy, and prolonged survival in mice bearing EGFRvIII-driven GBM. Our results uncover a relationship between cancer driver mutations, TIME composition, and sensitivity to checkpoint blockade in GBM and support the stratification of patients with GBM for checkpoint blockade therapy based on integrated genotypic and immunologic profiles.

Abstract PD2-04: Preclinical development of CodaLytic™, a codon-modified influenza virus, as a novel virotherapeutic agent for breast cancer immunotherapy

Abstract Multiple species of oncolytic viruses (OVs) have been shown to modulate the tumor microenvironment (TME) by increasing immune cell infiltration and activating stimulatory immune responses, leading to the induction of a tumor-specific immune response. Many engineered OVs achieve tumor specificity by either gene deletion or mutations and are then armed with immunomodulatory transgenes to promote anti-tumor immune responses. In an alternative approach, OVs derived from Codagenix’s codon/codon pair modification platform aim to leverage the natural immunostimulatory capacity of selected viral species for efficacy and take advantage of defects in innate immune sensing and apoptosis mechanisms in cancer cells as well as receptor overexpression for tumor selectivity. CodaLytic is a novel virotherapeutic derived from influenza virus strain A/California/07/2009, that is synthetically engineered to contain over 600 silent mutations in hemagglutinin and neuraminidase genes and is being developed as a novel immunotherapeutic for breast cancer. In the orthotopic EMT6 triple-negative breast cancer model, known for its moderate sensitivity to immunotherapies, intratumoral injection of 108 PFU three times a week for up to 4 weeks as a monotherapy led to significant tumor growth inhibition by 76% (p < 0.001 vs vehicle control), translating into a significant survival benefit with a 66% cure rate. Intravenous rechallenge of EMT6 long-term survivors led to a 27-fold reduction in lung nodule formation and a tumor-specific interferon-γ memory response was observed ex vivo in their splenocytes. Anti-tumor efficacy after CodaLytic treatment was accompanied by a change in the composition of the tumor immune infiltrate with significant increases in T, B and NK cells and increased gene expression of pathways and genes related to T cell effector function, dendritic cell activation, antigen presentation and chemoattraction. In immunotherapy-resistant orthotopic 4T1 tumors, combination of CodaLytic with a CTLA-4 inhibitory antibody, but not anti-PD-1 blockade – a combination that had demonstrated combination benefit in several other preclinical models – led to reduction in tumor growth by 75% (p < 0.0001 vs vehicle control and PD-1 combination group). Median overall survival improved from 22 to 30 days with addition of CTLA-4 blockade. Triple combination including PD-1 inhibition led to improved long-term survival beyond 50 days with 30% complete regressions. In summary, these preclinical data demonstrate CodaLytic’s ability to induce broad innate and adaptive changes in the breast cancer TME, resulting in anti-tumor efficacy and prolonged survival. Characterization of the tumor immune infiltrate after CTLA-4 combination and pharmacodynamic changes achieved after CodaLytic/checkpoint combination treatment in human breast cancer tumoroids will further support identification of correlates of efficacy with translational implications. Together with preclinical toxicology data and demonstrated clinical safety of this attenuated influenza virus after intranasal administration in healthy individuals, CodaLytic emerges as a promising novel viroimmunotherapeutic agent and is planned to enter a phase 1 clinical trial in early 2023. Citation Format: Marcin Stawowczyk, Yiwen Zhao, Katie Pfeffer, Juliana Tafrova, James Rodriguez, Chen Yang, Nusrat Jahan, Sybil A. Tasker, Steffen Mueller, J. Robert Coleman, Johanna K. Kaufmann. Preclinical development of CodaLytic™, a codon-modified influenza virus, as a novel virotherapeutic agent for breast cancer immunotherapy [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD2-04.

Retreatment of Patients With Metastatic Cutaneous Melanoma Who Relapse After Elective Checkpoint Inhibitor Discontinuation After a Complete Remission.

Checkpoint blockade has improved the response rate and survival in metastatic melanoma. Elective treatment discontinuation appears to be reasonable in most patients who have achieved a confirmed complete remission. It seems crucial to understand whether restarting immune checkpoint inhibitor therapy can induce additional responses or remissions in rare patients who relapse. A retrospective analysis identified only 10 patients who relapsed after elective treatment discontinuation after a radiologically confirmed remission. These patients were retreated with single-agent PD-1 or combined CTLA-4 plus PD-1-directed monoclonal antibodies. We found an initial complete response rate of 20% (2 patients) following retreatment. With a median follow-up of 26 months, the addition of individualized salvage therapies converted an additional 4 patients to a 2nd remission. All 6 of these patients have again discontinued therapy. Three patients have died of metastatic melanoma, while another is receiving salvage therapy. Six of our 10 patients experienced grades 2-3 retreatment-related toxicity. There were no hospitalizations or fatalities. Retreatment of relapsing patients resulted in 20% complete responses with checkpoint inhibitors. The planned addition of other treatment modalities converted another 4 patients (40%) to a durable 2nd remission. This sequential approach merits further exploration in prospective clinical trials.

Hypophysitis and Secondary Adrenal Insufficiency From Immune Checkpoint Inhibitors: Diagnostic Challenges and Link With Survival.

Hypophysitis is a serious adverse event stemming from immune checkpoint inhibitor (ICI) therapy for malignancy. This study aimed to characterize ICI-induced hypophysitis, identify diagnostic challenges, and evaluate an association with survival in a large cancer cohort. We performed a retrospective cohort study of adult patients with cancer who received ICIs between December 1, 2012, and December 31, 2019. We identified 839 patients who received CTLA-4, PD-1, or PD-L1 inhibitors or a combination thereof who were followed for a median of 19.4 months. Hypophysitis was defined as MRI evidence of pituitary gland and/or stalk enlargement or biochemical evidence of hypopituitarism if not explained by another etiology. A total of 16 (1.9%) patients developed hypophysitis a median of 7 months after ICI initiation, with most patients having melanoma (9/16; 56.2%) or renal cell carcinoma (4/16; 25%). Two patients also had exogenous glucocorticoid exposure but exhibited secondary hypothyroidism and secondary adrenal insufficiency (AI). Median age at the start of ICI was 61.3 years and 57% were men. Patients who developed hypophysitis were younger compared with those who did not develop hypophysitis (median age, 57 vs 65 years; P=.011). Hypophysitis occurred most frequently after combination therapy (13.7%) compared with CTLA-4 monotherapy (1.9%), PD-1 monotherapy (1.2%), and PD-L1 monotherapy (0.8%) (P<.0001). Pituitary gland enlargement on MRI occurred more frequently after CTLA-4 inhibitor monotherapy or combination therapy (5/7; 71.4%) compared with PD-1/PD-L1 inhibitor monotherapy (1/6; 16.7%). The survival benefit of hypophysitis was not apparent after addressing immortal time bias and adjusting for other variables affecting patient outcomes. Secondary AI occurred in all patients, and secondary hypothyroidism occurred in half. Classic pituitary gland enlargement is usually absent in PD-1/PD-L1 inhibitor-induced hypophysitis. Further pituitary evaluation must be conducted to differentiate secondary AI resulting from exogenous glucocorticoids and hypophysitis in patients with cancer receiving ICIs. The link between hypophysitis and ICI efficacy needs further investigation.

TEST ARTICLE: Hypophysitis and Secondary Adrenal Insufficiency From Immune Checkpoint Inhibitors: Diagnostic Challenges and Link With Survival.

Hypophysitis is a serious adverse event stemming from immune checkpoint inhibitor (ICI) therapy for malignancy. This study aimed to characterize ICI-induced hypophysitis, identify diagnostic challenges, and evaluate an association with survival in a large cancer cohort. We performed a retrospective cohort study of adult patients with cancer who received ICIs between December 1, 2012, and December 31, 2019. We identified 839 patients who received CTLA-4, PD-1, or PD-L1 inhibitors or a combination thereof who were followed for a median of 19.4 months. Hypophysitis was defined as MRI evidence of pituitary gland and/or stalk enlargement or biochemical evidence of hypopituitarism if not explained by another etiology. A total of 16 (1.9%) patients developed hypophysitis a median of 7 months after ICI initiation, with most patients having melanoma (9/16; 56.2%) or renal cell carcinoma (4/16; 25%). Two patients also had exogenous glucocorticoid exposure but exhibited secondary hypothyroidism and secondary adrenal insufficiency (AI). Median age at the start of ICI was 61.3 years and 57% were men. Patients who developed hypophysitis were younger compared with those who did not develop hypophysitis (median age, 57 vs 65 years; P=.011). Hypophysitis occurred most frequently after combination therapy (13.7%) compared with CTLA-4 monotherapy (1.9%), PD-1 monotherapy (1.2%), and PD-L1 monotherapy (0.8%) (P<.0001). Pituitary gland enlargement on MRI occurred more frequently after CTLA-4 inhibitor monotherapy or combination therapy (5/7; 71.4%) compared with PD-1/PD-L1 inhibitor monotherapy (1/6; 16.7%). The survival benefit of hypophysitis was not apparent after addressing immortal time bias and adjusting for other variables affecting patient outcomes. Secondary AI occurred in all patients, and secondary hypothyroidism occurred in half. Classic pituitary gland enlargement is usually absent in PD-1/PD-L1 inhibitor-induced hypophysitis. Further pituitary evaluation must be conducted to differentiate secondary AI resulting from exogenous glucocorticoids and hypophysitis in patients with cancer receiving ICIs. The link between hypophysitis and ICI efficacy needs further investigation.

Colon Adenoma After Diagnosis of Immune Checkpoint Inhibitor-mediated Colitis.

Purpose: While the occurrence of colitis during immune checkpoint inhibitor (ICI) treatment is recognized as a sign of robust immune activation and correlates with better oncological outcomes, the long-term impact of ICI-mediated colitis on the colonic mucosa has not been studied. We thus aim to describe the colonoscopy and histology findings in patients at a follow-up time of ≥ 6 months post initial colitis event. Methods: This retrospective analysis included adult cancer patients diagnosed with ICI colitis at a tertiary cancer center between October 2013 and June 2020. The study group included patients diagnosed with immune mediated colitis who had also undergone a follow up colonoscopy or flex sigmoidoscopy. The control group was patients exposed to ICI without immune mediated colitis. We reported patients' colitis clinical course, treatment, outcomes, and endoscopic and histologic features at diagnosis and at follow-up time of ≥ 6 months. Results: Total 39 patients met the study criteria, with 82% being male, and 35.8% having melanoma. Most patients received a combination of CTLA-4 and PD-1/L1 inhibitors (82%). On initial endoscopic evaluation, inflammation without ulceration was reported in 76.9% of patients and active inflammation on histologic examination in 79.3% of patients. Most patients (79.4%) received corticosteroids, and 56.4% received add-on selective immunosuppressive therapy. Four patients received fecal microbiota transplantation. On follow-up, new incidence of colonic polyps was reported in 51.2% of patients, including adenomas in 33.3% among the colitis patients with median follow up duration of 12 months. The incidence of adenoma polyps 12 months after the colitis event was significantly higher compared to the control group without colitis based on the time-to-event analysis (p=0.041). Conclusion: At a median follow up of 12 months after their initial colitis diagnosis, 51.2% of the patients had new incidence of colonic polyps, including a third with adenoma, at a significantly higher incidence than the control group without colitis. Studies with larger sample sizes are needed to further define the long-term impact of colitis and its treatments on colon health and to refine recommendations for surveillance of colonic adenomas and colorectal cancer.

Dual Immune Checkpoint Blockade and Hypofractionated Radiation in Recurrent/Metastatic Squamous Cell Carcinomas of the Head and Neck Previously Treated with Immune Checkpoint Inhibitors

<h3>Purpose/Objective(s)</h3> This single arm open label phase II study sought to explore the safety and antitumor activity of combined antiPDL1 and CTLA4 blockade with hypofractionated radiation (XRT) in patients with recurrent/metastatic head and neck squamous cell carcinomas (RMHNSCC) who have previously been treated with an immune checkpoint inhibitor (ICI). <h3>Materials/Methods</h3> Patients with RMHNSCC who progressed on prior ICI, ECOG 0/1, a bone or lung metastatic site amenable to XRT and RECIST 1.1 measurable disease apart from the radiated site were eligible. Durvalumab 1500mg IV x 13 doses and tremelimumab 75mg IV x 4 doses were both administered every 4 weeks. Hypofractionated image-guided (HIGRT) or stereotactic (SBRT) XRT was given in 3 fractions every other day to a total dose of 24 Gy starting week 2. The primary endpoint was safety; secondary endpoints were RECIST 1.1 responses in non-radiated measurable lesions and overall survival (OS). Blood was obtained at baseline and at week 4 for flow cytometric peripheral T cell analysis. The accrual goal was 20 patients with the first 6 patients representing a safety run in cohort. This project was approved by our institutional IRB and registered at clinicaltrials.gov (NCT035225). <h3>Results</h3> Between August 2018 and November 2020, 6 patients were enrolled, followed by study closure by the sponsor due to funding. All patients were male, 4 white and 2 Asian, with a median age of 64 years (range 47-67), 4 had oropharynx, 1 oral cavity and 1 hypopharynx as primary sites, 5 were never smokers. All patients had progressed on ICI in the R/M setting (2 nivolumab, 2 pembrolizumab, 1 avelumab and 1 durvalumab). Five patients completed XRT: 4 to lung lesions and 1 to a superior mediastinal LN, no toxicities attributed to the radiation were observed. One patient was unable to receive XRT due to progression. Only 2 patients completed more than 4 treatment cycles (median 2.5, range 1-13 cycles). One dose limiting toxicity (recurrent Grade 2 diarrhea) was observed. Four grade 3 toxicities (neck pain due to tumor, shingles, dyspnea due to disease progression and fatigue) were observed in 3 patients, one of which was deemed treatment related (fatigue). Among 5 evaluable pts, we observed 1 complete response (CR), 3 stable disease (SD), 1 disease progression (PD). The patient with a CR showed an increase in PDL1+ and PD1+ T cells at 4 weeks, which was not observed in the 3 other evaluable patients with PD and SD. With one surviving patient in follow up for 14 months, median OS was 8 months (range 4-14). <h3>Conclusion</h3> In this small study population of previously ICI treated RMHNSCC, durvalumab, tremelimumab and XRT resulted in expected toxicities and limited efficacy. Increase in peripheral PDL1+ and PD1+ T cells may correlate with response and may merit further study.

S879 IL12/23 Blockade for Refractory Immune-Mediated Colitis: A Case Series From Two Centers

Introduction: Ustekinumab, a human monoclonal antibody to the interleukin (IL) 12/23 p40 subunit, is efficacious in the management of severe inflammatory bowel disease (IBD). Immune-mediated colitis (IMC) is a common immune checkpoint inhibitors (ICIs) toxicity that is similar to IBD. Robust data on optimal evidence-based management of IMC is lacking, and current medical therapy includes steroids, followed by infliximab (IFX) and/or vedolizumab (VDZ). Fecal microbiota transplantation (FMT) is used for colitis refractory to aforementioned therapies. To explore the efficacy of ustekinumab in managing refractory IMC, we present a case series of 19 patients who developed IMC and were treated with the same. Methods: This is a retrospective chart review of cancer patients from two tertiary care centers who received ICI therapy and developed IMC refractory to standard of care treatments and were treated with ustekinumab. Clinical remission is defined as improvement in IMC grade to ≤ 1, and response as any improvement in GI symptoms. Results: Of 19 patients in our cohort, the majority were Caucasians females with a median age of 63 years. The most common cancer type was melanoma (52.7%). Nine (47%) patients had received combination CTLA-4/PD-1 regimens prior to onset of IMC. Most (84.2%) patients had grade ≥3 diarrhea and 42.1% had ulcerative inflammation. All patients’ IMC remained clinically refractory to systemic steroids and IFX and/or VDZ, prompting initiation of ustekinumab. 13 (68.4%) improved following ustekinumab. Sixteen patients (84.2%) had clinical remission at last follow up. Eight patients in our cohort received FMT, 4 before and 4 after ustekinumab, six of whom improved after ustekinumab. (Table) Conclusion: IMC can be refractory to multiple lines of therapy including corticosteroids, IFX, VDZ, or FMT. IL12/23 inflammatory pathway may serve as a therapeutic target in managing such cases. The majority of patients in our case series had improvement in their IMC symptoms following ustekinumab, and only one patient experienced an adverse event. This result shows promise for the use of IL12/23 antagonists in the management of refractory IMC case, but further studies are still needed to validate its use. Table 1. - Characteristic Data (N=19) Highest grade of diarrhea (3-4) – no. (%) 16 (84.2%) Highest grade of colitis (2-4) – no. (%) 13 (68.3%) Initial endoscopic findings—no (%) Ulcers 8 (42.1%) Non-ulcer inflammation 5 (26.3%) Normal 6 (31.6%) Hospitalizations – no. (%) 14 (73.7%) Other treatment of GI adverse event – no. (%) Steroid 19 (100%) Infliximab 11 (57.9%) Vedolizumab 18 (94.7%) FMT 8 (42.1%) Number of ustekinumab doses, median (IQR) 2 (10.5%) 1 dose of ustekinumab 7 (36.8%) >1 dose of ustekinumab 12 (63.2%) Clinical remission following ustekinumab treatment –no (%) 13 (68.4%) Clinical remission of colitis at last follow-up - n=19 16 (84.2%)

Hitting the sweet spot: optimal use of corticosteroids for immune checkpoint inhibitor side-effects

Since the approval of ipilimumab for the treatment of melanoma in 2011, immune checkpoint inhibitors have changed the treatment landscape for solid and haematological malignancies,1 and almost half of patients with cancer might be eligible for treatment with these drugs.2 A substantial number of those treated with immune checkpoint inhibitors will have so-called immune-related adverse events: rates of such adverse events range from approximately 15% for PD-1 and PD-L1 inhibitors to approximately 35% for CTLA-4 antibodies and approximately 55% for the combination of CTLA-4 and PD-1 antibodies.

Development of a nanoparticle-based immunotherapy targeting PD-L1 and PLK1 for lung cancer treatment

Immune checkpoint inhibitors (ICIs) targeting PD-L1 and PD-1 have improved survival in a subset of patients with advanced non-small cell lung cancer (NSCLC). However, only a minority of NSCLC patients respond to ICIs, highlighting the need for superior immunotherapy. Herein, we report on a nanoparticle-based immunotherapy termed ARAC (Antigen Release Agent and Checkpoint Inhibitor) designed to enhance the efficacy of PD-L1 inhibitor. ARAC is a nanoparticle co-delivering PLK1 inhibitor (volasertib) and PD-L1 antibody. PLK1 is a key mitotic kinase that is overexpressed in various cancers including NSCLC and drives cancer growth. Inhibition of PLK1 selectively kills cancer cells and upregulates PD-L1 expression in surviving cancer cells thereby providing opportunity for ARAC targeted delivery in a feedforward manner. ARAC reduces effective doses of volasertib and PD-L1 antibody by 5-fold in a metastatic lung tumor model (LLC-JSP) and the effect is mainly mediated by CD8+ T cells. ARAC also shows efficacy in another lung tumor model (KLN-205), which does not respond to CTLA-4 and PD-1 inhibitor combination. This study highlights a rational combination strategy to augment existing therapies by utilizing our nanoparticle platform that can load multiple cargo types at once.

The Risk of Opportunistic Infections and the Role of Antibiotic Prophylaxis in Patients on Checkpoint Inhibitors Requiring Steroids.

Immune-related adverse events (irAEs) often require treatment with high-dose systemic steroids (SS) and other immunosuppressive agents (ISAs). NCCN Guidelines recommend prophylactic antibiotics for Pneumocystis jirovecii pneumonia (PJP) for patients receiving prolonged SS/ISAs. However, there is a paucity of evidence regarding the incidence of opportunistic infections (OIs) and non-OIs and the role of prophylactic antibiotics in patients on SS/ISAs for irAEs. A retrospective analysis was conducted of patients treated using immune checkpoint inhibitor (ICI) therapy at 5 MedStar Health hospitals from January 2011 to April 2018. OIs were defined per the Infectious Diseases Society of America guidelines for the prevention and treatment of OIs in patients with HIV. The study cohort included patients who received ≥20 mg daily of a prednisone equivalent for ≥4 weeks to manage irAEs. The study cohort identified 112 (15%) of 758 total patients treated using ICIs. Baseline characteristics included the following: median age was 64 years, 74% (n=82) of patients were White, 89% (n=100) had an ECOG performance status ≤1, 61% (n=68) had melanoma, 19% (n=21) had non-small cell lung cancer, 45% (n=50) were treated using an anti-PD-(L)1 ICI, and 33% (n=37) were treated using an anti-PD-1/anti-CTLA-4 combination. The median starting SS dose was 100 mg of a prednisone equivalent, and 25% of patients required additional ISAs, with infliximab (n=15) and mycophenolate mofetil (n=9) being the most common. We found that 20% (n=22) of patients developed any infection, including 7% (n=8) with OIs (oral candidiasis [n=4], nondisseminated varicella zoster infection [n=2], PJP [n=1], and Listeria monocytogenes endophthalmitis [n=1]) and 13% (n=14) with non-OIs (most common: Clostridium difficile and pneumonia [n=5 each]). PJP prophylaxis with sulfamethoxazole/trimethoprim was given to 13% (n=14) patients, of whom 43% (n=6) developed OIs/non-OIs. Our study highlights the fundamental issues for patients on ICI therapy who require SS/ISAs for irAEs: the degree of immunosuppression and the relative risk of OI. We noted a low incidence of OIs overall and breakthrough infections despite PJP prophylaxis. We question whether PJP prophylaxis is efficacious or necessary. Prospective trials are required to answer these questions.

Symptomatic melanoma metastases in the brain: are we using all therapy options?

In recent years, significant advances have been made in systemic therapy for patients with metastatic melanoma of the skin, resulting in an increase in one-year overall survival (OS) from 25 to 85% and 5-year OS from less than 10 to 60% in certain patient subgroups. Approximately 50% of patients with metastatic skin melanoma are diagnosed with metastatic brain lesions in the course of the disease. Modern drug therapy for metastatic brain lesions is slowly but surely proving to be effective. Thus, in the presence of a mutation in the BRAF gene, BRAF inhibitor monotherapy provides an intracranial objective response rate (iORR) of 25 to 40%, whereas BRAFi + MEKi combined targeted therapy (CTT) achieves already 58% iORR, including in patients with symptomatic metastases to the brain. However, the duration of responses achieved on targeted therapy (TT) is shorter than for extracranial disease prevalence. On the other hand, regardless of the presence of a BRAF mutation, immunotherapy (PD-1 monotherapy) achieves a response in approximately 20-22% of patients, but these responses are more durable, although fewer than on TT. The combination of CTLA-4 + PD-1 checkpoint inhibitors produces long-lasting responses with a iORR of 51-54%. However, the achievement of these results and an overall increase in life expectancy with immunotherapy is mostly possible in symptom-free patients and in patients receiving low or no doses of glucocorticosteroids (10 mg or less on prednisolone). Therefore, for symptomatic patients, especially those whose tumors have been identified with a BRAF mutation, a combination of targeted therapy, which would quickly achieve an objective response in 58%, and anti-PD1/PDL1 immunotherapy, which is likely to increase the duration of the response achieved and give a chance for a sustained remission, looks promising. This article provides an overview of key studies and our own experience with the triple combination in metastatic brain lesions.