Randomized phase II trial of lymphodepletion plus adoptive cell transfer of tumor-infiltrating lymphocytes, with or without dendritic cell vaccination, in patients with metastatic melanoma

BACKGROUND

The adoptive transfer of tumor-infiltrating lymphocytes (TIL) has demonstrated robust efficacy in metastatic melanoma patients. Tumor antigen-loaded dendritic cells (DCs) are believed to optimally activate antigen-specific T lymphocytes. We hypothesized that the combined transfer of TIL, containing a melanoma antigen recognized by T cells 1 (MART-1) specific population, with MART-1-pulsed DC will result in enhanced proliferation and prolonged survival of transferred MART-1 specific T cells in vivo ultimately leading to improved clinical responses.

DESIGN

We tested the combination of TIL and DC in a phase II clinical trial of patients with advanced stage IV melanoma. HLA-A0201 patients whose early TIL cultures demonstrated reactivity to MART-1 peptide were randomly assigned to receive TIL alone or TIL +DC pulsed with MART-1 peptide. The primary endpoint was to evaluate the persistence of MART-1 TIL in the two arms. Secondary endpoints were to evaluate clinical response and survival.

RESULTS

Ten patients were given TIL alone while eight patients received TIL+DC vaccine. Infused MART-1 reactive CD8⁺ TIL were tracked in the blood over time by flow cytometry and results show good persistence in both arms, with no difference in the persistence of MART-1 between the two arms. The objective response rate was 30% (3/10) in the TIL arm and 50% (4/8) in the TIL+DC arm. All treatments were well tolerated.

CONCLUSIONS

The combination of TIL +DC showed no difference in the persistence of MART-1 TIL compared with TIL therapy alone. Although more patients showed a clinical response to TIL+DC therapy, this study was not powered to resolve differences between groups.

TRIAL REGISTRATION NUMBER

NCT00338377.

Intrathecal (IT) and intravenous (IV) nivolumab (N) for metastatic melanoma (MM) patients (pts) with leptomeningeal disease (LMD)

9519

Background: MM pts with LMD have a dismal prognosis, with median overall survival (OS) < 3 months, no approved therapies and extremely limited clinical trial options. We previously reported initial safety findings from an open label, single arm, single center phase I/IB trial (NCT03025256), in which IT and IV N were well tolerated, without any CNS-specific or unexpected toxicity. Here we report an update on safety and maximum tolerated dose (MTD) for all patients enrolled, and efficacy for the completed dose cohorts. Methods: MM patients aged >18 with evidence of LMD by MRI and/or CSF cytology, ECOG PS ≤2 were treated with IT and IV N. Dexamethasone ≤4mg/daily and concurrent BRAF/MEK inhibitor(i) treatment was allowed. For cycle 1, IT N was administered via intraventricular reservoir on day (D)1. For subsequent cycles (every 14 days), pts received IT N on D1, followed by IV N 240 mg on D2. IT N doses evaluated were 5, 10, 20 mg and 50 mg. Blood and CSF were collected at multiple time points for translational research. The primary objectives of this first-in-human study were to determine the safety and MTD of IT N given with IV N in MM pts with LMD. Bayesian mTPI methodology was used to define the MTD. Results: To date, 23 pts have been treated: two at 5, three at 10, fourteen at 20 mg and four at 50 mg IT N. Median age at LMD diagnosis was 42 (28-73); 12 pts are male. All pts had radiographic evidence of LMD and neurological symptoms; 14 pts had positive CSF cytology at baseline. 21 pts received prior therapies for their metastatic melanoma: anti-PD1 (n = 19), BRAFi/MEKi (n = 14), chemo (n = 2), IT IL2 (n = 4) other (n = 2). 19 pts had prior XRT, including whole brain RT (n = 7). Two pts were treatment-naïve. The median number of IT N doses was five (1- 66). The combination regimen was well tolerated by all evaluable pts (n=23), with only five pts (22%) experiencing gr 3 AEs, and no reported gr 4 or 5 toxicities. Nausea (30%), diarrhea (26%), and rash (22%) were the most common AEs. Eight pts (23%) experienced AEs after IT N administration, all gr 1. Initial efficacy analysis included only pts (n=19) treated with first three dose levels (5-20mg). Median follow-up for these pts is 4.5 months (mos) (1.1, 31.5 mos) and median OS is 63 % at 3 mos, 42 % at 6 mos and 30% at 12 mos. Conclusions: The trial demonstrates the feasibility and safety of IT administration of modern immunotherapy for MM pts with LMD. No unexpected systemic or neurological toxicity was observed with 20mg IT N. 2 additional patients are required to complete the 50mg IT N cohort. OS rates at 6 and 12 mos are encouraging and support further evaluation of IT administration of immunotherapy agents for pts with MM and LMD. Final presentation will include results of LMD for all dose cohorts, composite response assessment and comparative analysis of longitudinal CSF samples to assess immunologic effects. Clinical trial information: NCT03025256.

Comprehensive genomic profiling of malignant peritoneal mesothelioma (MPeM) reveals key genomic alterations (GAs) distinct from malignant pleural mesothelioma (MPM)

8557

Background: MPeM is a rare and aggressive cancer with very limited treatment options. Lack of dedicated research has impeded improvements in outcomes. Defining prevalent GAs is a critical unmet need for use of targeted therapies in these patients. Although MPeM is notably distinct from MPM vis-à-vis epidemiologic and clinical attributes, the genomic underpinings of these differences have yet to be established. We aimed at describing a comprehensive genomic profile (CGP) of MPeM in comparison to MPM. Methods: We performed a retrospective comparative analysis between 89 patients with MPeM and 241 patients with MPM (N = 330) who underwent CGP using CLIA certified next-generation sequencing assays. The cohort was generated using mesothelioma patients at MD Anderson Cancer Center (N = 223) and supplemented by additional mesothelioma patients (N = 107) from a publicly available database from Memorial Sloan Kettering Cancer Center, the MSK-IMPACT database. Essential clinicopathological variables were collected. Descriptive statistics, Fisher’s exact and Mann-Whitney tests were used for comparison. Kaplan-meier method and log rank tests were used for overall survival (OS) estimates. Results: MPeM cohort (vs. MPM) had more women (54% vs. 31%, P < 0.001) and younger age at diagnosis (56 vs. 69 years, P < 0.001). Histology was epithelioid, biphasic and sarcomatoid in 86%, 7% and 7% cases, a distribution similar to MPM cohort. At least 1 GA was found in 64 (72% vs. 82% in MPM, P = 0.044) of MPeM patients with a median of 1 (range 1 – 12) (vs. a median of 2, range 1 – 24, P < 0.001) GA per patient. A significantly lower proportion of MPeM patients had ≥ 3 mutations (14% vs. 26%, OR 2.1, P = 0.028) per patient. The most frequent mutations were present in the following genes: TP53 (24%), BAP1 (16%), NF2 (15%), MET (9%) and TRAF7, KIT and PIK3CA (each 6%). MPeM patients harbored more mutations in MET (9% vs. < 1%, P < 0.001) and TRAF7 (6% vs. < 1%, P = 0.02) but fewer mutations in BAP1 (16% vs. 32%, P = 0.003) and CDKN2B (0% vs. 5%, P = 0.041). The most common copy number variations (CNVs: amplifications or deletions) were seen in BAP1, MCL1, SETD2, WT1 (each 2%) and AURKA (1%) genes. Among genes with CNVs, MPeM had a lower rate of deletions in CDKN2A (1% vs. 6%, P = 0.040). Among more common GAs, only BAP1 mutations appeared to be associated with poor OS (45.7 vs. 127.1 months, HR 2.5, 95%CI: 0.6 – 10.1, P = 0.050) in patients with MPeM. Conclusions: In this large cohort with CGP, we identified potential molecular drivers in MPeM and demonstrated key genomic differences between MPeM and MPM. MPeM is frequently driven by GAs involved in cell cycle control, a potentially targetable pathway. Despite this insight from CGP, a large subset of patients do not have actionable GAs and for these patients, further collaborative trans-“omic” research efforts are needed to advance potential therapeutic options.

Extrapleural Pneumonectomy versus Pleurectomy/Decortication for Malignant Pleural Mesothelioma

BACKGROUND

Whether extrapleural pneumonectomy (EPP) or extended pleurectomy/decortication (P/D) is the optimal resection for malignant pleural mesothelioma (MPM) remains controversial. We therefore compared perioperative outcomes and long-term survival of patients who underwent EPP vs P/D.

METHODS

Patients with the diagnosis of MPM who underwent either EPP or P/D from 2000 to 2019 were identified from our departmental database. Propensity score matching was performed to minimize potential confounders for EPP or P/D. Survival analysis was performed by the Kaplan-Meier method and Cox multivariable analysis.

RESULTS

Of 282 patients, 187 (66%) underwent EPP and 95 (34%) P/D. Even with propensity score matching, perioperative mortality was significantly higher for EPP than for P/D (11% vs. 0%; P=0.031), when adjusted for perioperative mortality, median overall survival between EPP and P/D was 15 vs. 22 months, respectively (P=0.276). Cox multivariable analysis for the matched cohort identified epithelioid histology (hazard ratio [HR], 0.56; P=0.029), macroscopic complete resection (HR, 0.41; P=0.004), adjuvant radiation therapy (HR, 0.57; P=0.019), and more recent operative years (HR, 0.93; P=0.011)-but not P/D-to be associated with better survival. Asbestos exposure (HR, 2.35; P=0.003) and pathological nodal disease (HR, 1.61; P=0.048) were associated with worse survival.

CONCLUSIONS

In a multimodality treatment setting, P/D and EPP had comparable long-term oncological outcomes, although P/D had much lower perioperative mortality. The goal of surgical cytoreduction should be macroscopic complete resection achieved by the safest operation a patient can tolerate.

A phase II study of sitravatinib (Sitra) in combination with nivolumab (Nivo) in patients (Pts) undergoing nephrectomy for locally-advanced clear cell renal cell carcinoma (accRCC)

312

Background: Sitra is a spectrum-selective receptor tyrosine kinase inhibitor (TKI) that targets TAM receptors (TYRO3, AXL, MERTK), VEGFR2, c-Kit, and MET. These receptors regulate several immune suppressive cell types in the tumor microenvironment, including M2-polarized macrophages, MDSCs, and T regulatory cells, which are implicated in resistance to checkpoint inhibitors. ccRCC is characterized by upregulation of VEGF and overexpression of MET and AXL. Sitra may combine effectively with immune checkpoint inhibition to augment antitumor activity in ccRCC. About 39% of patients with accRCC who receive surgery with curative intent relapse representing an unmet need in this setting. Together these data support the evaluation of neoadjuvant sitra with nivo in accRCC. Methods: This phase II study (NCT03680521) evaluated sitra and nivo in pts with locally- advanced ccRCC who were candidates for curative nephrectomy. Single-agent sitra (120 mg) was administered daily (QD) for 2 weeks, with nivo (240 mg intravenously Q2W) added to sitra for 4-6 weeks. A plan for potential dose de-escalation was implemented using a modified toxicity probability interval method with a maximum toxicity of 20% at the tolerated dose. Pts underwent pathology/tissue evaluation at 3 timepoints: biopsy prior to treatment, biopsy prior to the addition of nivo, and nephrectomy specimen evaluation at time of nephrectomy. The primary endpoint was objective response (RECIST 1.1); secondary endpoints included safety, PK, and correlative immune effects (selected protein and gene expression and immune cell populations). Results: A total of 20 pts were evaluated for safety (95% had T3 or higher stage tumors, 65% with baseline hypertension). Dose-limiting toxicities (DLTs) led to a dose de-escalation, resulting in 7 pts treated at 120 mg QD sitra and 13 pts treated at 80 mg QD. DLTs included grade 3 (Gr3) hypertension (n=6); deep vein thrombosis and pulmonary embolism (Gr3) were observed in 1 additional pt. Median duration of sitra treatment was 6.3 weeks at the 80 mg dose and 7.1 weeks at the 120 mg dose. With a median follow-up of 9.4 months after initiation of systemic therapy, no pts have relapsed. In 17 pts evaluable for efficacy, the investigator-assessed confirmed ORR was 11.8%, including 2 PRs (33.3% ORR in pts who received 120 mg sitra). No pts experienced progressive disease while on therapy. Median DFS was not reached. There was 1 delayed surgery due to nivo-related thyroiditis that resolved. Reported TRAEs: Gr1/Gr2 in 55% of pts (dysphonia 50%, fatigue 45%, diarrhea 40%, hypertension 30%, increased ALT 30%), Gr3 in 45% of pts (hypertension 30%). There were no Gr4/Gr5 TRAEs. Correlative blood and tissue analyses will be presented. Conclusions: The combination of sitra and nivo is clinically active with a manageable safety profile as a neoadjuvant therapy for accRCC. Clinical trial information: NCT03680521 .

T-cell agonists in cancer immunotherapy

Cancer cells can evade immune surveillance in the body. However, immune checkpoint inhibitors can interrupt this evasion and enhance the antitumor activity of T cells. Other mechanisms for promoting antitumor T-cell function are the targeting of costimulatory molecules expressed on the surface of T cells, such as 4-1BB, OX40, inducible T-cell costimulator and glucocorticoid-induced tumor necrosis factor receptor. In addition, CD40 targets the modulation of the activation of antigen-presenting cells, which ultimately leads to T-cell activation. Agonists of these costimulatory molecules have demonstrated promising results in preclinical and early-phase trials and are now being tested in ongoing clinical trials. In addition, researchers are conducting trials of combinations of such immune modulators with checkpoint blockade, radiotherapy and cytotoxic chemotherapeutic drugs in patients with advanced tumors. This review gives a comprehensive picture of the current knowledge of T-cell agonists based on their use in recent and ongoing clinical trials.

Abstract PR03: Nongenomic BAP1 aberrancy drives highly aggressive cutaneous melanoma phenotype

The purpose of this study was to determine the role of BAP1 levels in cutaneous melanoma (CM). BAP1 is a tumor suppressor in which loss of heterozygosity (LOH) from mutation and copy number alteration is well described in germline and somatic cancers. Although BAP1 genomic alterations in CM are extremely rare (2% of 665 samples from 5 datasets), marked variability in BAP1 expression is observed in CM. We show that low nuclear BAP1 levels portend a significantly worse clinical outcome in stage III CM (n=37, log rank p ≤0.01 for both overall survival and progression-free survival). Gene Set Enrichment Analysis (GSEA) revealed low BAP1 expression to be most highly ranked with an increased epithelial–mesenchymal transition (EMT) gene expression profile in CM tumors (n=379, FDR q = 1.34E-26) and cell lines (n=53, FDR q = 2.86E-116). We identify the expression of ZEB1, a master regulator of EMT, to be significantly associated with low BAP1 expression in CM tumors and cell lines (p= 1.5E-04 and 3.3E-05, respectively). Analysis of the BAP1 promoter indicates three canonical ZEB1 binding sites. Functional experiments show ZEB1 to bind to the BAP1 promoter, and luciferase activity assays indicate that ZEB1 acts as a transcriptional suppressor of BAP1 expression with differential utilization of the promoter binding sites. Targeted reduction of endogenous ZEB1 caused increased BAP1 levels, while targeted reduction of BAP1 did not modulate ZEB1 levels, consistent with ZEB1 having a suppressive effect on BAP1. Phenotypically, targeted reduction of BAP1 in CM cells resulted in a switch from a more differentiated, melanocytic state, to a less differentiated, more migratory and invasive phenotype. Extinguishing melanocyte-specific BAP1 in mice with a BRAF V600E mutant genetic background resulted in the emergence of primary melanoma tumors, with a marked EMT gene expression profile, and resultant metastases. Given the phenotypic changes associated with BAP1 levels in our mouse and human studies, we then tested the effect of modulating BAP1 on BRAF targeted therapy. Exogenous expression of BAP1 sensitized BRAF inhibitor (vemurafenib)-resistant melanoma cells, while the targeted reduction of BAP1 desensitized BRAF inhibitor-sensitive melanoma cells. BRAF mutant/BAP1 loss mice failed to exhibit a marked response to vemurafenib treatment compared to control mice. These data implicate regulation of BAP1 to be a major mechanism that characterizes a highly malignant and treatment-resistant subset of tumors. Our study indicates that nongenomic reduction in BAP1 through ZEB1 transcriptional modulation may be a key factor in aggressive CM.

This abstract is also being presented as Poster A30.

Citation Format: Haifeng Zhu, Junna Oba, Xiaoxing Yu, Caitlin A. Creasy, Marie-Andrée Forget, Fernando Carapeto, Cara L. Haymaker, Chang-Jiun Wu, Tatiana V. Karpinets, Wei-Lien Wang, Michael T. Tetzlaff, Alexander J. Lazar, Gordon B. Mills, Amanda R. Moore, Yu Chen, Jianhua Zhang, Jeffrey E. Gershenwald, Jennifer A. Wargo, Chantale Bernatchez, Patrick Hwu, P. Andrew Futreal, Scott E. Woodman. Nongenomic BAP1 aberrancy drives highly aggressive cutaneous melanoma phenotype [abstract]. In: Proceedings of the AACR Special Conference on Melanoma: From Biology to Target; 2019 Jan 15-18; Houston, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(19 Suppl):Abstract nr PR03.

Peripheral cytokines are not influenced by the type of surgical approach for non-small cell lung cancer by four weeks postoperatively

OBJECTIVES

The influence of surgical approach on systemic inflammatory response and the subsequent oncologic impact for non-small cell lung cancer is debated. We aimed to measure the effects of thoracic surgical approach on peripheral cytokine milieu over time.

METHODS

Patients undergoing primary lung resection without neoadjuvant therapy (2016-2018) were evaluated. A panel of 43 cytokines, angiogenic factors, and inflammatory molecules (CAFs) were evaluated in peripheral blood preoperatively, at 24 -hs and 4-weeks postoperatively. Differences between CAFs in patients undergoing thoracotomy versus video-assisted thoracoscopic surgery (VATS) at all timepoints were assessed using Student's t-test.

RESULTS

76 patients with available peripheral CAF panels met inclusion criteria. Thoracotomy was performed in 53 (70 %) patients while VATS was undertaken in 23 (30 %). Upon examination of known inflammatory CAFs, including IL-1β, IL-6, IL-8, IL-10, IFN-γ, and soluble (s) CD27, no differences were detected at 24 h or 4 weeks postoperatively between surgical groups. Examination of trends over time did not demonstrate any temporal derangements for these CAFs, with return to baseline levels by 4 weeks postoperatively for both groups. Evaluation of soluble (s) checkpoint molecules, including sPD-1, sPD-L1, sTIM-3, and sCTLA-4, did not reveal any differences in the immediate postoperative or long-term recovery period.

CONCLUSIONS

Peripheral immune profiles following pulmonary resection do not appear to differ between VATS and thoracotomy postoperatively. CAF fluctuations are transient and recover rapidly. These results, at the peripheral cytokine level, suggest that the surgical approach for lung cancer is unlikely to alter the effectiveness of novel immune-modulating systemic therapies, although more studies are needed to validate these findings.

Abstract D075: Investigating the immuno-biology underlying differential response to immunotherapy in White and non-White patients with metastatic acral melanoma

Background: Acral melanoma (ACML), the rarest form of melanoma (MEL) represents 4-6% of all MEL cases however it is the most common subtype darker pigmented individuals accounting for up to 70% of all cases. Checkpoint inhibitors (CPI) have emerged as an efficacious treatment option. In cutaneous melanoma (CtMEL), tumor mutational burden (TMB) correlates with response rate. Despite low TMB in AMEL, responses to CPI parallel those in CtMEL. Given the differences in ethnicity among ACML patients compared CtMEL patients we aimed to study: (i) the correlation between response and TMB, (ii) the relationship between ethnicity and response and (iii) the underlying immune-biology accounting for differential responses. Method: All advanced and metastatic ACML patients (pts) treated with anti-CTLA4 (ipilimumab) or anti-PD1 (pembrolizumab or nivolumab) immunotherapy between March 2011 and January 2019 at MD Anderson Cancer Center, Texas, were included in this retrospective analysis. Clinical response, progression free survival and overall survival (PFS and OS) and their correlation to ethnicity and TMB were evaluated. Objective response was measured using RECIST 1.1 and analyzed using logistic regression. PFS and OS were assessed using the Kaplan Meir method and log-rank test. TMB was predicted using validated algorithm based on a defined gene mutation set obtained using next generation sequencing. Results: 44 pts with Stages III-IV ACML (IIIA: 2%, IIIB 9%, IIIC 27%, IV-M1A: 16%, IV-M1B: 25%, IV-M1C: 20%, IV-M1D2%) were included in the analysis. Median age was 63 years old (39-88) and 60% were men. Of 44 patients 12 (27%) self-identified as Hispanic, 2 as (5%) Asian and 30 (68%) as White. The overall response rate was nearly 5 times times higher in Hispanic compared to White pts (OR 4.60, p-value 0.04). The median TMB in Hispanic patients was 16 mutations/mb compared to 7 mutations/mb in White pts. The median PFS and OS for White pts were 7.2 months and 34.3 months respectively while for Hispanic pts the median PFS and OS were 6.7 (log-rank p=0.69) and 26.1 months (log-rank p=0.38) respectively. In addition to this data deep immune analysis of tumor tissue including nanostring, gene expression and TCR sequencing will be assessed and reported. Conclusions: The data from this small retrospective study suggests that White pts with ACML had low response rates to CPI presumably due to low TMB while interestingly, Hispanic pts, despite relatively low TMB have high response rates paralleling those seen in the overall CtMEL population. Despite higher response rates in Hispanic patients, there was no significant difference in OS. This data together with further immune analysis provides the rationale to design prospective studies to investigate how tumor micro-environment varies with ethnicity. Additionally we will investigate the social and biological determinants that limit survival in Hispanic pts despite higher response rates.

Citation Format: Kaysia Ludford, Chantal Saberian, Sara K Nabhan, Stephen Gruschkus, Chantale Bernatchez, Natalie Jackson, Cara L Haymaker, Patrick Hwu, Adi Diab. Investigating the immuno-biology underlying differential response to immunotherapy in White and non-White patients with metastatic acral melanoma [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr D075.

CIMAC-CIDC CyTOF harmonization

e15242

Background: The Cancer Immune Monitoring and Analysis Centers – Cancer Immunology Data Commons (CIMAC-CIDC) network is a National Cancer Institute-funded initiative to identify biomarkers of mechanisms and response to cancer immunotherapy clinical trials, using state-of-the-art assay technologies. A primary platform for CIMAC-CIDC biomarker studies is CyTOF mass cytometry, which is performed at all four CIMAC laboratories. Methods: To test the ability to generate comparable data across labs, a cross-site harmonization effort was undertaken. We first harmonized SOPs between centers. Because of a new acquisition protocol introduced by the vendor (Fluidigm), we also tested this protocol across sites before finalizing the harmonized SOP. We then performed a cross-site assay harmonization experiment, using 5 shared cryopreserved PBMC samples and one lyophilized control cell preparation, along with a shared lyophilized antibody cocktail consisting of 14 markers, as validated in the HIPC consortium, plus CD45. These reagents and samples were distributed to the four sites, and FCS files were centrally analyzed by both manual gating and automated methods (Astrolabe). Results: Average CVs across sites for each cell population were reported and compared to a previous multisite CyTOF study. Once a cell recovery issue at two sites was resolved, this experiment resulted in inter-site reproducibility of under 20% CV for most cell subsets, very similar to the previous study. Conclusions: These results emphasize the ability to reproduce CyTOF across sites, and also highlights procedures, such as use of spike-in control samples, useful for tracking variability in this assay.

Single-center phase I/Ib study of concurrent intrathecal (IT) and intravenous (IV) nivolumab (N) for metastatic melanoma (MM) patients (pts) with leptomeningeal disease (LMD)

10008

Background: MM pts with LMD have a dismal prognosis, with a median overall survival (OS) < 3 months and no approved therapies. IT administration of interleukin-2 (IL2) achieves survival in ~15% of MM LMD pts, but at cost of severe toxicities. Given the favorable clinical activity and safety of systemic anti-PD1, we hypothesized that IT N administration is safe and can achieve clinical benefit in pts with LMD. Methods: The primary objectives of this first-in-human study (NCT03025256) were to determine the safety and the maximum tolerated dose (MTD) of IT N given with IV N in MM pts with LMD. Eligible pts had MM, ECOG PS < / = 2, and evidence of LMD by MRI and/or CSF cytology. Dexamethasone < / = 4mg/daily was allowed. For cycle 1, IT N is administered via intraventricular reservoir on day (D) 1; Blood and CSF is collected at multiple time points for translational research. For subsequent cycles (every 14 days), pts receive IT N on D1, followed by IV N 240 mg on D2. IT N doses evaluated were 5, 10, and 20 mg. Bayesian mTPI methodology was used to define the MTD. The study was recently amended to allow for concurrent BRAF/MEK inhibitor(i) treatment. Results: To date, 15 pts have been treated: two at 5, three at 10, and 10 at 20 mg IT N. Median age at LMD diagnosis was 41.8 (30.9-73.2) years; 6 pts are male. All pts had radiographic evidence of LMD and neurological symptoms; 8 pts had positive CSF cytology. 12 pts received prior therapies for their MM: anti-PD1 (n = 11), BRAFi/MEKi (n = 9), chemo (n = 2), IT IL2 (n = 4) other (n = 2). 11 pts had prior XRT, including whole brain RT (n = 7). 1 pt was treatment-naïve. The median numbers of IT N doses was 4 (1-42). No grade (Gr) 4-5 AEs were attributed to IT N or IV N; only 4 events (Gr 1, n = 2; Gr2, n = 2) were possibly related to the IT N. With a median follow-up of 18.7 weeks (1-83.3 wks), the median OS is 46.1 weeks (0.1-83.3). Clinical response data, translational research endpoints, including changes in CSF cytokines and cfDNA, will be reported. Conclusions: The trial demonstrates the feasibility of prospective clinical trials in MM patients with LMD. The combination of IT/ IV N was safe and well-tolerated, with no unexpected systemic or neurological toxicity. Final presentation will include results of LMD composite response assessment, comparative analysis of longitudinal CSF/blood samples to assess immunologic effects. Finally, the interim OS of the patients is encouraging, and supports further evaluation of IT administration of immunotherapy agents for pts with MM and LMD. Clinical trial information: NCT03025256.

Successful tumor-infiltrating lymphocyte (TIL) growth from uveal melanoma (UM) using a three-signal (3.0) method

3027

Background: Metastatic UM is a rare cancer with poor response rates to systemic therapy. Adoptive transfer of patient-specific TIL may represent the best strategy for treatment. TIL are harvested from primary or metastatic tumors and initially expanded in culture with high dose IL-2 prior to undergoing rapid expansion protocol and therapeutic administration. Here, we report improved rates of initial expansion using a previously described TIL 3.0 method which utilizes dual agonistic antibodies to TCR and 4-1BB (Urelumab) for stimulation, respectively, with high dose IL-2, compared to the traditional method. Methods: Between 2006 and 2019, patients were consented for TIL harvest from either primary or metastatic UM tumors. Demographics, clinical features, and outcomes of the TIL initial expansion were collected. Success rates, number of cells expanded, and days in culture for the two methods were analyzed using partially overlapping samples t-tests and z-tests. Results: There were 85 harvests and expansions from 76 patients using the traditional method and 32 expansions from 30 patients using TIL 3.0. Initial TIL expansion was successful in 97% of TIL 3.0 harvests compared to 35% for the traditional method (p < 0.001). More TIL were expanded with TIL 3.0 compared to the traditional method (291.3 million cells vs. 88.6 million cells, p < 0.001), and fewer days were required in culture (18.5 vs. 29.0, p < 0.001). Both primary UM harvests and metastatic harvests were more successful with TIL 3.0 (90% vs. 12% for primary, p < 0.001, and 100% vs. 42% for metastatic, p < 0.001). Conclusions: Expansion of UM tumors via the TIL 3.0 method led to successful growth in 97% of harvests. Therapeutic administration to patients with TIL 3.0 is under active investigation. [Table: see text]

Abstract 4062: Activation of innate and adaptive immunity using intratumoral tilsotolimod (IMO-2125) as monotherapy in patients with refractory solid tumors: a phase Ib study (ILLUMINATE-101)

While checkpoint inhibitor therapy has transformed treatment of multiple tumor types, many patients remain refractory. Tilsotolimod, a toll-like receptor 9 agonist, has been shown in preclinical models to activate plasmacytoid dendritic cells and increase T cell infiltration to the tumor microenvironment. Preliminary results of a phase 1/2 study suggested that intratumoral injection of tilsotolimod in combination with ipilimumab may revive an immune response in patients with immune checkpoint inhibitor-resistant metastatic melanoma. To further explore the role of tilsotolimod in modulating the tumor immune microenvironment, we conducted a Phase Ib monotherapy trial (ILLUMINATE-101). Adults with histologically or cytologically confirmed diagnosis of cancer not amenable to curative therapies received intratumoral tilsotolimod in doses escalating from 8 mg to 32 mg into a single lesion at weeks 1, 2, 3, 5, 8, and 11. Objectives of the dose evaluation portion included characterizing safety and pharmacokinetics, and evaluating alterations in the tumor microenvironment. Blood samples and tumor biopsies of injected and distal lesions were obtained at baseline and on treatment. Immune analyses included evaluation using Nanostring and/or flow cytometry of activation of the type 1 interferon (IFN) pathway, IFN gamma levels, activation of dendritic cell subsets, and changes in T cell status. As of November 7, 2018, 41 patients have been enrolled, including 38 patients into the dose evaluation portion and 3 patients into a melanoma expansion cohort. No dose-limiting toxicities or treatment-related adverse events have been observed. Within 24 hours, fresh tumor biopsies showed significant increases in IFN gamma levels, activation of the type 1 IFN pathway, induction of an antigen processing gene signature (a measure of the MHC class I antigen presentation pathway), and maturation of dendritic cells as measured by expression of HLA-DR (MHC class II), compared to pretreatment biopsies. Of 25 evaluable patients who received at least 1 dose of tilsotolimod and had at least 1 post-baseline disease assessment, 12 (48%) had a RECIST v1.1 disease assessment of stable disease. For patients with at least one disease assessment following documentation of stable disease (n=8), duration of stable disease ranged from 0.53 to 4.2+ months, with 3 patients ongoing. These results demonstrate that single agent tilsotolimod was well tolerated and induced robust alterations in the tumor microenvironment.

Citation Format: Hani M. Babiker, Vivek Subbiah, Orla Maguire, Shah Rahimian, Hans Minderman, Cara L. Haymaker, Chantale Bernatchez, Erkut Borazanci, James Geib, Srinivas K. Chunduru, Peter M. Anderson, Igor Puzanov, Adi Diab. Activation of innate and adaptive immunity using intratumoral tilsotolimod (IMO-2125) as monotherapy in patients with refractory solid tumors: a phase Ib study (ILLUMINATE-101) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4062.

Association of relative neutrophilia with a distinct immunoinhibitory milieu in non-small cell lung cancer

e14047

Background: Elevated neutrophil-to-lymphocyte ratio (NLR) has been associated with poor prognosis in non-small cell lung cancer (NSCLC); the biological underpinnings of this observation have not been fully elucidated. We examined the relationships between peripheral neutrophil counts (PMN), NLR, circulating cytokines and angiogenic factors (CAF), and tumor microenvironment (TME) features in NSCLC. Methods: 150 patients with resectable NSCLC were enrolled in an immunoprofiling project. A panel of 43 CAFs was used to analyze preoperative plasma samples. Chemotherapy-naïve patients with CAF and a complete blood count ≤30 days preoperatively were included (n = 66; Table). For a subset, transcriptional signatures (MCP-counter, n = 50) and flow cytometry (n = 19) were used to identify TME phenotypes. Results: Increased PMNs were associated with increased pro-inflammatory CAF such as IL-1b (r = 0.392) and IL-6 (r = 0.339), as well as Th17/Tc17 associated CAF IL-17A (r = 0.320) and TNF-a (r = 0.368). Elevated NLR was inversely correlated with the lymphocyte activation marker soluble CD27 (r = -0.320, p = 0.009). This negative association was mirrored in the TME, as tumor neutrophil signatures were inversely correlated with a local IFN-g gene signature (r = -0.626, p < 0.001). Interestingly, a Th17/Tc17 peripheral signature (elevated IL-17A) was associated with an enrichment of CD8+TIM3+ cells (r = 0.623, p = 0.042) in the tumor. While this requires confirmation in a larger cohort, this correlation provides a potential rationale for targeting TIM3 in this population. Upon analysis of clinical characteristics, peripheral PMNs and NLR were higher among patients with squamous histology (PMN p = 0.009; NLR p = 0.034) and positively correlated with tumor size (PMN r = 0.344, p = 0.004; NLR r = 0.363, p = 0.003). Conclusions: A relative neutrophilia in NSCLC patients is associated with an inflammatory milieu suggestive of a Th17/Tc17 presence and decreased lymphocyte activation that is reflected within the TME. Further investigation is needed to define the role of NLR as a predictive biomarker and to identify whether neutrophils or Th17/Tc17 T cells could serve as a therapeutic target to improve immunotherapy response in NSCLC.[Table: see text]

Phase II trial of nab-paclitaxel (ABI) and ipilimumab (ipi) in patients with treatment naïve metastatic melanoma

9554

Background: Conventional chemotherapies possess intrinsic immune-regulatory properties. Some taxanes for instance, stimulate antigen presentation and impair regulatory T-cells while leaving effector T cells intact. Combining chemotherapies with immune checkpoint inhibitor at carefully designed dosing regimens may increase tumor cell susceptibility to immune-mediated death and thus enhance therapeutic efficacy. We describe the safety and updated efficacy of ABI and ipi in patients with metastatic melanoma. Methods: In this open-label, single center, phase II trial, ABI was administered to treatment naïve metastatic patients at 150mg/m2 on days 1,8 and 15 every 4 weeks and ipi at 3mg/kg on day 1 every 3 weeks limited to 4 cycles until disease progression or unacceptable toxicity. Endpoints included ORR, OS and safety. Results: 18 of 21 enrollees between 6/2013 and 6/2015 with Stage IV melanoma (M1c: 56%, M1b: 33%, M1a: 11%) were included in the analysis. The median age was 57 years old (33-69) and 67% were men. 44% harbored BRAF mutations. Median duration of treatment was 9 weeks (5 to 17). Median follow-up time for OS analysis was 22.5 months (2 to 52 months). 12 and 24 month OS were 77.8% and 60.6% respectively with median not yet reached. The ORR by by irRECIST was 27.8%. Grade 3 adverse events were reported in 50% of patients, the most common being neutropenia. 17% of patients had grade 3 immune-related adverse events, the most common being hypophysitis and colitis. Immune analysis showed absolute lymphocyte count was significantly elevated post treatment compared with pre-treatment (p = 0.024). In addition, deep immune analysis of peripheral blood samples and tumor tissue including nanostring, gene expression and TCR sequencing will be assessed and reported. Conclusions: The combination of ipi and ABI in this small study demonstrates acceptable safety, tolerability and clinical activity. ABI may contribute to tumor cytoreduction and enhance antitumor clinical response of ipi without impactful immunosuppression. This data together with further immune analysis may provide rationale to design prospective chemo-immunotherapy regimens and treatments for metastatic melanoma and other solid tumors. Clinical trial information: NCT01827111.

Lymphodepletion (LD), tumor-infiltrating lymphocytes (TIL) and high (HD-IL2) versus low-dose (LD-IL2) IL-2 followed by pembrolizumab (pembro) in patients (pts) with metastatic melanoma (MM)

9543

Background: TIL adoptive cell transfer (ACT) therapy can produce durable responses for MM pts although efficacy appears lower in the era of checkpoint inhibitors. Toxicities from HD-IL2, including sepsis physiology, limits widespread use of this regimen. Suppression of transferred TIL by either tumor cells or the tumor microenvironment could limit TIL responses. Pembro is known to promote T cell activation, thus, we evaluated the efficacy and safety of TIL with pembro with HD-IL2 versus LD-IL2. Methods: Pts with MM who had tumor harvested and cryopreserved TIL at MD Anderson with PS 0-1 and normal organ function were eligible. All pts received a standard LD regimen consisting of cyclophosphamide and fludarabine, followed by infusion of pooled ex-vivo expanded TIL and either HD-IL2 (Arm 1: 720,000 IU/kg IV q 8 hrs up to 15 doses) or LD-IL2 (Arm 2: 2 million IU SC for 14 d). Pts received pembro 200mg IV starting 21 d post T cell infusion every 3 wks for up to 2 yrs. Pts were randomized 1:1 based on stage and LDH. Paired blood and tumor biopsies were obtained prior to LD, prior to first and second dose of pembro and at time of progression. Results: A total of 36 pts were planned to enroll (18 in each arm); however, the protocol met pre-specified futility boundaries in Arm 1 which prompted early closure after treatment of 14 pts (7 in each Arm). Median age was 50 yrs, 6 were female, 8 had cutaneous melanoma, 2 mucosal, 2 uveal and 2 unknown primary. 86% were stage M1c, 14% M1D, 50% had LDH elevation. Median lines of prior therapy were 3 (range 1-6), including prior anti PD-1 in 13 pts. Best overall response was 1 PR (for 10 mos), 2 SD, 3 PD, 1 NE in Arm 1; 1 PR (ongoing over 36 mos), 1 SD, 5 PD in Arm 2. With median follow up of 9.2 mos, PFS was 3.9 mos for Arm 1 and 2.1 mos for Arm 2 (p = 0.99). Median OS was 9.7 mos for Arm 1 and 8.8 mos for Arm 2 (p = 0.71). Toxicity was similar in both Arms but with lower rates of grade 3 febrile neutropenia (57% vs. 71%) and shorter hospital stay (median 16 vs. 18 d) in Arm 2 vs. Arm 1. Conclusions: In a heavily treated pt population, TIL with pembro achieved low response rates. Use of LD-IL2 did not diminish efficacy and may be better tolerated than HD-IL2 for TIL ACT. Correlative studies are ongoing to determine mechanisms of treatment response and failure. Clinical trial information: NCT02500576.

T cell repertoire analysis of non-small cell lung cancer patients treated with neoadjuvant nivolumab alone or in combination with ipilimumab (NEOSTAR trial)

8532

Background: Neoadjuvant immune checkpoint inhibitors (ICIs) are being explored in resectable non-small cell lung cancer (NSCLC). Here, we studied the composition and changes in the T cell repertoire in a cohort of NSCLC patients (n = 44) treated with neoadjuvant nivolumab (N) alone or in combination with ipilimumab (NI) followed by surgery (NEOSTAR trial). Methods: Sequencing of the variable CDR3β chain of the T cell receptor (TCR) involved in antigen binding was performed in pre-treatment and surgical tumors, matched adjacent uninvolved lung specimens, as well as paired longitudinal blood at baseline, prior to each dose of therapy, prior to surgery, and within 8 weeks post-surgery. T cell repertoire density, diversity, and clonality (reactivity) were evaluated in addition to tumor PD-L1 expression pre- and post-neoadjuvant treatment. Results: Median T cell diversity in the blood post-therapy was 3.3-fold higher in NI- compared to N-treated patients (40,993 [NI, n = 3] vs 12,177 [N, n = 4] unique TCR rearrangements, n.s.). However, median T cell clonality in the blood was 3.5-fold higher in N- than NI-treated patients post-therapy (0.093 [N, n = 4] vs 0.026 [NI, n = 3], n.s.). Median clonality was 3.8-fold higher in the tumor post-therapy in patients receiving NI than in those receiving N (0.076 [NI, n = 7] vs 0.020 [N, n = 5], n.s.). Interestingly, diversity in the blood at baseline and in the tumor post-therapy were positively correlated ([n = 7], r = 0.82; p = 0.023), which may reflect an influx of cells from the periphery following ICIs. Importantly, higher baseline T cell clonality in the blood was associated with a lower % of viable tumor at time of surgery in both treatment arms ([n = 7], r = -0.77; p = 0.04). Conclusions: Our study is the first to assess the TCR repertoire in NSCLC patients treated with combination neoadjuvant NI and highlights potential mechanistic differences compared to N alone. Neoadjuvant NI is associated with higher clonality in tumors and lower clonality in blood post-therapy, suggesting increased T cell trafficking into the tumor. Finally, lower pre-treatment clonality in the periphery was correlated with higher % viable tumor post-neoadjuvant ICIs. Clinical trial information: NCT03158129.

Adoptive transfer of tumor-infiltrating lymphocytes in patients with sarcomas, ovarian, and pancreatic cancers

TPS2650

Background: Adoptive cell therapy (ACT) with tumor-infiltrating lymphocytes (TIL) has a long history of efficacy in metastatic melanoma, and is being increasingly considered across other solid tumors. Preclinical data generated at MD Anderson Cancer Center has demonstrated the ability to grow TIL from a variety of tumor types including various types of sarcomas, ovarian and pancreas cancers. We are testing the efficacy of TIL across multiple tumor types using two different manufacturing protocols. Methods: We are conducting two ongoing investigator initiated basket TIL therapy trials. The first (NCT03449108) includes cohorts with poorly differentiated soft tissue and bone sarcomas, osteosarcoma, and platinum resistant ovarian cancer. The TIL product used in this trial is an investigational cell product (LN-145, Iovance Biotherapeutics, Inc.). The second trial (NCT03610490) includes cohorts of osteosarcoma, platinum resistant ovarian cancer, and pancreatic cancer (who have progressed on, or received maximal benefit from, front-line therapy). For this trial, TIL are manufactured at MD Anderson Cancer Center using a protocol that includes the use of urelumab (an agonistic anti-CD137 antibody) combined with T cell receptor activation during TIL expansion. In both trials eligible subjects undergo tumor harvest using a surgical excisional biopsy of the tumor for TIL manufacturing, receive a modified cyclophosphamide and fludarabaine lymphodepletion regimen and up to six doses of IL-2 (600,000 IU/kg) following TIL infusion. No intervening therapy is allowed between tumor harvest and initiation of lymphodepletion. The primary endpoint for each cohort is ORR as assessed by investigators using RECIST 1.1 criteria. The Simon’s two stage design is used to monitor the efficacy of each cohort independently. In the first stage, 10 patients will be treated per cohort. If there is no confirmed response in these 10 evaluable patients, the cohort will be terminated. If the cohort moves forward to Stage II, an additional 8 patients will be treated leading to a total of 18 patients. Three or more responders out of 18 treated patients for the cohort will be considered clinically relevant to justify further investigation. Enrollment is ongoing in all cohorts in both trials. An accrual update will be provided at the annual meeting. Clinical trial information: NCT03449108, NCT03610490.

Interleukin-6 is potential target to de-couple checkpoint inhibitor-induced colitis from antitumor immunity

2616

Background: A deep understanding of the immunobiology of checkpoint inhibitor (CPI) induced immune related toxicities, such as immune related enterocolitis (irEC), and how these compare to the immune signatures in tumors could lead to the development of strategies that de-couple autoimmunity from anti-tumor immunity. Methods: Total RNA from patient-matched irEC and normal colon FFPE tissue from patients [n = 12] receiving CPIs were profiled with the 770 gene NanoString nCounter PanCancer Immune Profiling Panel (NanoPCIP). The mean fold change in gene expression from normal vs. irEC inflamed colonic tissue and baseline vs. on-treatment tumor samples from patients responding or non-responding to ipilimumab based therapy were analyzed. C57BL/6 mice with B16.BL6 melanoma tumors were treated with systemic anti-IL-6 + anti-CTLA-4 vs. anti-CTLA4 alone vs. placebo and tumor size was measured. Results: In patients with irEC, the highest significantly upregulated differentially expressed gene (DEG) in inflamed colon tissue encoded for IL-6 (Fold change +24.1). None of the significant and highest upregulated DEGs in the colitis, including IL-6, were significantly upregulated in responding tumors. Interestingly, IL-6 was also the highest upregulated DEG in non-responding tumors numerically. When comparing mean fold changes across these analyses, the gene with the largest difference in upregulatation between colitis and responding tumors was IL-6; the other highest upregulated genes in colitis encoded for neutrophil and monocyte chemotactic molecules. In our mouse models, the addition of IL-6 blockade to anti-CTLA-4 therapy significantly improved tumor shrinkage compared to anti-CTLA-4 alone. Conclusions: Our data demonstrates that IL-6-mediated inflammation may be more prevalent in irEC and tumors not responding to CPIs than in tumors responding, and blocking IL-6 enhances CPI anti-melanoma activity. Targeting IL-6 may ameliorate irEC without hindering anti-tumor immunity.

Phase Ib clinical investigation of intraperitoneal ipilimumab and nivolumab in patients with peritoneal carcinomatosis due to gynecologic malignancy

TPS5606

Background: The peritoneal cavity is a frequent site of metastasis and recurrence for gynecologic malignancy, including approximately 80% of epithelial ovarian cancer (EOC) that presents with peritoneal involvement. These observations have led to the use of intraperitoneal (IP) route of administration for traditional cytotoxic chemotherapy. IP immunotherapy is a recognized but under explored area of clinical investigation with many potential advantages. Indeed, IP administered antibodies in both animals and human subjects are associated with absent or much lower peripheral blood concentrations. In addition to higher local and lower systemic exposure, other theoretical advantages include preferential binding to intraperitoneal and intratumoral immune cells, and absorption through the draining lymphatics of the peritoneal cavity. These pelvic and peri-aortic lymph nodes represent the most relevant lymphoid organs and as such may be the ideal site for T cell activation and trafficking back to the peritoneal tumor. Methods: The trial (NCT03508570) is a single-institution phase Ib trial to determine the recommended phase II dosing (RP2D) of IP administration of nivolumab in combination with ipilimumab. For the purpose of dose finding, the assessment period for dose limiting toxicity (DLT) is 12 weeks. The trial starts with a safety lead-in to confirm the safety of IP nivolumab before combining it with ipilimumab. A maximum sample size of 12 will be used to find the RP2D for nivolumab, up to 24 patients for the combination, and a planned expansion will be carried out such that at least 12 EOC patients are treated at RP2D of the intraperitoneal combination strategy. The secondary objectives are to describe the pharmacokinetics and toxicities, and to estimate the clinical benefit rate for the expansion cohort. Translational objectives include description of immunologic and biologic changes in serial blood and IP fluid collections as well as pre and on-treatment biopsies. Eligibility criteria include recurrent or progressive biopsy-confirmed platinum resistant EOC or other gynecologic cancer with measurable peritoneal disease, and no exposure to prior treatment with checkpoint inhibition. Enrollment began in January of 2019 with 3 subjects enrolled to date. Accrual update will be provided at the annual meeting. Clinical trial information: NCT03508570.

A preclinical study of tumor-infiltrating lymphocytes in NSCLC

161

Background: Multiple clinical studies have shown that adoptive cell transfer (ACT) of autologous tumor-infiltrating lymphocytes (TIL) is remarkably effective in melanoma patients. Non-small cell lung cancer (NSCLC) shares similarities with melanoma in terms of mutational burden and sensitivity to immune checkpoint inhibitors. We therefore sought to test whether TIL ACT may represent a viable option for the treatment of NSCLC patients. We utilized tissue collected from patients enrolled on the prospective ImmunogenomiC prOfiling of Non-small cell lung cancer (ICON) study. Methods: TIL and tissue-infiltrating lymphocytes were expanded ex vivo from 97 freshly resected early-stage localized NSCLC tumors and 39 matched uninvolved lung tissues. Growth and functional characteristics of TIL were assessed via flow cytometry, TIL-tumor reactivity assays, and analysis of TCRβ sequencing data. Results: NSCLC showed an increased proportion of CD3+ lymphocytes within the tumor-infiltrating leukocyte component as compared to matched normal lung tissue. The TIL compartment included a suppressed CD8+ T cell subset expressing significantly higher levels of PD-1 and lacking cytolytic potential compared to T cells expanded from normal tissue. TIL contained a higher proportion of proliferating (Ki67+) CD8+CD103+ tissue-resident memory (TRM) cells expressing activation markers such as CTLA4, LAG3, PD1 and ICOS, and increased CD4+ Tregs. Despite a highly immunosuppressive environment, TIL expansion was achieved with a success rate of 68% (n = 97) but appeared hindered in patients undergoing neoadjuvant chemotherapy treatment prior to surgery (56.2%, n = 16 vs 72.5% success rate in therapy-naïve patients). In addition, expansion efficiency (number expanded and time of culture) of TIL and matched lung residing lymphocytes were significantly associated (r = 0.379, p = 0.017, n = 39). Importantly, expanded CD8+ TIL products were oligoclonal and showed reactivity toward autologous tumors. Conclusions: Although NSCLC TIL are functionally inhibited in vivo they can be successfully expanded ex vivo and demonstrate recognition of autologous tumor cells. These data suggest that TIL can potentially be used for adoptive T cell-based immunotherapy in NSCLC.

Preclinical development of tumor-infiltrating lymphocyte therapy for metastatic colorectal cancer

95

Background: Immunotherapy has become an effective cancer therapy, particularly in the case of checkpoint blockade and adoptive T-cell therapy (ACT). ACT exploits the presence of tumor-infiltrating lymphocytes (TIL) by exponentially expanding their numbers ex vivo and re-infusing them into the patient in an autologous setting. With the effectiveness of TIL therapy already well established in multiple phase II studies in melanoma, there is a push to translate it to other cancers in need of improved therapies. Colorectal cancer (CRC) is a cancer where the presence of TIL has been strongly correlated with increased survival. Metastatic CRC (mCRC) has a poor outcome with median overall survival of less than 3 years. At present anti-PD1 therapy is only active in the small subset of mCRC patients (4%) that are MSI-high. We sought to evaluate the ability to generate and characterize TIL from patients with mCRC to provide a rationale for future TIL therapy in this disease. Methods: To assess the feasibility of utilizing TIL ACT for this patient population, we characterized the immune infiltrate of mCRC, TIL growth from tumor fragments (n = 24), as well as the TIL repertoire (n = 4) and anti-tumor potential in samples with available autologous tumor target. Results: Flow cytometry analysis detected a CD4-rich T-cell infiltration at the tumor site as well as a scarce yet activated CD8+ TIL population. The outgrowth of CD8+ TIL from tumor fragments in media containing IL-2 was potentiated by the addition of an agonistic 4-1BB antibody (Urelumab, BMS). Additionally, the use of a 4-1BB mAb improved the likelihood of growing TIL (63% [14/24] to 83% [20/24]) and increased the total yield of TIL grown. T-cell receptor sequencing showed enrichment in the tumor of CD8+ T-cell clones shared between the blood and tumor, suggesting selective expansion at the tumor site. Using IFNγ ELISPOT, CD8+ TIL from one patient with an MSS tumor were found to be reactive against a peptide derived from mutated TP53R116W restricted to HLA-B*39:01. Conclusions: It is possible to expand CD8+ T cells from microsatellite stable (MSS) mCRC that are able to target tumor antigens. Although preliminary, the initial data suggest the feasibility of TIL therapy for mCRC.