Nanobiotix (France)

Preclinical syngeneic tumor models are widely used to evaluate therapeutic responses in immunocompetent hosts, particularly for radiotherapy and radio-immunotherapy. Standard models, such as CT26.WT mouse colorectal carcinoma, have provided valuable insights into treatment efficacy and immune modulation. However, they often fail to reproduce the complexity of advanced human cancers, especially metastases, which differ from primary tumors in immunogenicity, antigen presentation, and tumor microenvironment (TME). Metastatic lesions are typically characterized by poor cytotoxic T cell infiltration and enrichment of immunosuppressive populations such as regulatory T cells and myeloid-derived suppressor cells, limiting the translational relevance of conventional approaches. To better model these features, we developed CT26.MtC3, a novel cell line derived from pulmonary metastases generated by systemic injection of CT26.WT cells into BALB/c mice. When implanted subcutaneously, CT26.MtC3 tumors displayed greater aggressiveness than parental CT26.WT. Immune profiling revealed a strongly immunosuppressive TME, with reduced CD8⁺ T cell infiltration and increased myeloid populations. Complementary in vitro analyses confirmed intrinsic differences, including higher migratory capacity, and significant upregulation of CAECAM-1a. Upon irradiation, CT26.MtC3 cells also showed altered expression of immune-regulatory molecules such as CD47, Fas, PD-L1, and PD-L2, potentially contributing to their immunoevasive phenotype in vivo. Together, these findings establish CT26.MtC3 as a clinically relevant model of metastatic, immune-resistant colorectal cancer. This model provides a robust platform for evaluating strategies to overcome tumor immunoresistance and for rigorously testing the potential of radio-immunotherapy combinations in settings that better reflect clinical reality.

ABSTRACT The annual ImmunoRad Conference has established itself as a recurrent occasion to explore the possibility of combining radiation therapy (RT) and immunotherapy (IT) for clinical cancer management. Bringing together a number of preclinical and clinical leaders in the fields of radiation oncology, immuno-oncology and IT, this annual event fosters indeed essential conversations and fruitful exchanges on how to address existing challenges to expand the therapeutic value of RT-IT combinations. The 8th edition of the ImmunoRad Conference, which has been held in October 2024 at the Weill Cornell Medical College of New York City, highlighted exciting preclinical and clinical advances at the interface between RT and IT, setting the stage for extra progress toward extended benefits for patients with an increasing variety of tumor types. Here, we critically summarize the lines of investigation that have been discussed at the occasion of the 8th Annual ImmunoRad Conference.

6035 Background: Overcoming resistance to immune checkpoint inhibitors (ICIs) is a major clinical challenge. NBTXR3, a novel radioenhancer composed of functionalized hafnium oxide nanoparticles administered by a single intratumoral injection, locally amplifies radiotherapy (RT) dose without adding toxicity to surrounding healthy tissue. NBTXR3/RT enhances tumor cell death, tumor antigen release, and effectively expands T-cell repertoire in preclinical models, thus potentially triggering local and systemic immune responses to help improve ICI treatment. NBTXR3 has demonstrated favorable local control in pts with LA-HNSCC. Here we report early outcomes from the ongoing Study 1100 trial in pts with locoregionally recurrent (LRR) or metastatic (M+) head & neck squamous cell carcinoma (HNSCC) who were either naïve to or who continued anti-PD-1 therapy combined with NBTRX3/RT after primary or secondary resistance to anti-PD-1 alone. Methods: A phase I dose escalation/expansion trial [NCT03589339] evaluating NBTXR3/Stereotactic Body RT (SBRT) followed by nivolumab or pembrolizumab in 3 cohorts of pts with advanced solid tumors. Pts have H&N lesions either resistant to prior ICI or naïve, or lung, liver, or soft tissue metastases from ICI-resistant advanced solid tumors. SBRT doses were: HN 35 Gy/ 5 fxns; lung 45 Gy/ 5 fxns; liver 45 Gy/ 3 fxns; soft tissue as per investigator. Primary objective is safety of NBTXR3/RT/anti-PD-1 combination and its RP2D. Secondary objectives include efficacy. Results: The RP2D was 33%. There were 55 pts with HNSCC treated in the dose escalation/expansion parts. NBTXR3 injection was feasible and safe. There were 11pts (20%) who experienced G≥3 treatment related AEs, of which 3 pts experienced G≥3 AEs (5.5%) related to NBTXR3. Preliminary results of 33 pts, who were evaluable for efficacy: are reported. 6 pts with LRR disease: (2 ICI resistant, 4 naïve);. 27 pts with M+ disease (18 ICI resistant, 9 naïve). In ICI-resistant pts, objective tumor responses were observed in 25% (5/20), and the disease control rate (DCR) was 75% (15/20). In the ICI-naïve population, objective tumor responses were observed in 54% (7/13) of pts and DCR was 77% (10/13). There were observed improvements in injected lesions as well as in some noninjected target lesions. Updated efficacy data including OS in resistant and naïve pts will be presented. Conclusions: NBTXR3/RT/anti-PD-1 combination was feasible and well tolerated. Early data suggest the addition of NBTXR3/RT to ICI showed evidence of efficacy, including in patients who failed prior ICI, opening up an opportunity to further explore the ability of NBTXR3/RT to mitigate primary or secondary resistance to ICI. Clinical trial information: NCT03589339 .

Abstract Patients with LAPC or BRPC often receive radiation therapy (RT) after chemotherapy (chemo) if no metastatic progression has occurred. Historically, CA19-9 normalizes in ~20 to 30% of patients after all therapy. While escalated dose radiotherapy (EDR) has shown promising survival in selected patients, extending use of EDR to all patients is challenging due to RT dose limitations of the bowel. To overcome this limitation, we are investigating NBTXR3, composed of functionalized hafnium oxide nanoparticles administered by a single intratumoral injection, locally amplifying the RT dose. In this phase 1 trial, the primary objective is to determine the NBTXR3 recommended phase 2 dose (RP2D). Secondary objectives are to measure anti-tumor effects. The study uses a Bayesian optimal interval design (BOIN) and has two parts: dose-finding (NBTXR3 at [level 1] 33% of gross tumor volume [GTV] or [level 2] at 42% of GTV) and cohort expansion at RP2D. In part 1, eligibility criteria included only LAPC patients with no evidence of metastatic disease after 2-6 months of chemo, part 2 allows BRPC. NBTXR3 was administered once prior to RT via an EUS-guided intratumoral injection. All patients received 45 Gy in 15 fractions with intensity modulated radiation therapy (IMRT). Patients were followed up to 1 year. Dose-limiting toxicities (DLTs) were defined as any grade ≥ 3 adverse events definitely or possibly related to NBTXR3 and/or RT. Target tumor response was per RECIST v1.1 criteria. CA19-9 was measured serially. We defined CA19-9 normalization as a value of 37 U/ml after finishing NBTXR3/RT. We compared rates of CA19-9 normalization in this phase 1 trial to a historical cohort of patients who received modern chemo/RT without NBTXR3. As of July 12, 2023, 15 LAPC patients have been treated with NBTXR3/RT. The median age was 63 years [range 43-81], 8 males, 7 females. The first patient (level 1) and subsequent 14 patients (level 2) had no injection complications. Level 2 had 1 non-serious DLT related to RT. At 4 weeks post RT, 13 had stable disease (SD) locally (2 had progressive disease [PD] overall), 1 had PD locally, and 1 had radiographic complete response (CR). At 3 months post RT, 11 had SD locally (1 PD overall), 1 PD locally, and 1 had surgery with negative margins and no residual viable tumor. 9 patients had elevated CA19-9 before NBTXR3/RT, 7 of these 9 (78%) had a decrease in CA19-9 subsequently, and 2 of these 9 (22%) had CA19-9 normalization eventually. 12 patients had elevated CA19-9 at diagnosis, and 5 out of 12 patients (42%) had normalization of CA19-9 after all therapy. We reviewed 455 patients with LAPC/BRPC between 2015-2019 who were treated at our institution as a comparison cohort for CA19-9 normalization rates. Out of 307 patients with elevated CA19-9 at diagnosis and normal bilirubin, 95 normalized (31%) and 212 did not normalize (69%) within 6 months of receiving cytotoxic therapy. The RP2D of NBTXR3 is 42% of GTV. The responses and CA19-9 results in comparison to historical data suggest promising anti-tumor efficacy of NBTXR3/RT. Citation Format: Gabriela Fuentes, Maria J. Rodriguez, Matthew H.G. Katz, Naruhiko Ikoma, Ching-Wei D. Tzeng, Michael Overman, Shubham Pant, Michael S. Lee, Robert A. Wolff, Milind Javle, Cullen M. Taniguchi, Emma B. Holliday, Ethan B. Ludmir, Prajnan Das, Albert C. Koong, Omar I. Vivar, Suyu Liu, Eric P. Tamm, Leonard A. Farber, Manoop S. Bhutani, Eugene J. Koay. Phase I study of endoscopic ultrasound (EUS)-guided NBTXR3 delivery activated by radiotherapy (RT) for locally advanced or borderline resectable pancreatic cancer (LAPC or BRPC) [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B002.

BackgroundNumerous recent studies have assessed the future direction of radiation oncology. Now more than ever there is a need to examine the changing landscape of novel agents and approaches that improve radiation efficacy as well as amplify the immune response with certain therapies. Immune checkpoint inhibitors (ICIs) have led to improved treatment outcomes in a variety of cancers, however many patients exhibit resistance. Overcoming this resistance is a major challenge in immuno-oncology. Radiation therapy (RT) has emerged as a promising combination with ICIs since it may act in some settings to produce an immunomodulatory effect. NBTXR3, a radioenhancer, is injected one time intratumorally and activated by RT. NBTXR3 increases RT energy deposition inside tumor cells, subsequent tumor cell death, and tumor antigen release and thus in combination with ICI may overcome resistance.MethodsPre-Clinical: Abscopal assays were conducted in immunocompetent mice. Anti-PD-1 sensitive or resistant lung tumor cell lines were injected in both flanks. Intratumoral injection of NBTXR3 (or vehicle) followed by RT was performed in right flank (primary) tumors only. Some mice also received anti-PD-1 injections. Tumor growth was monitored, and tumor immune cell infiltrates analyzed by immunohistochemistry (IHC).ClinicalA multicenter phase I trial [NCT03589339] is evaluating NBTXR3/RT/anti-PD-1 in 3 cohorts of patients with advanced solid tumors eligible for anti-PD-1: 1) Locoregional recurrent or recurrent and metastatic HNSCC, 2) Lung metastases, or 3) Liver metastases. NBTXR3 was administered by intratumoral injection. Stereotactic body RT (SBRT) was delivered at tumor-site selective doses per standard practice.ResultsPre-clinical studies demonstrated that NBTXR3/RT induces an immune response not observed with RT alone and enhances systemic control. IHC showed significant increase of CD8+ T-cell infiltrates in both NBTXR3/RT treated, and untreated tumors. Furthermore, NBTXR3/RT/anti-PD-1 improved local and systemic control in mice bearing anti-PD-1 resistant lung tumors, produced long-term memory, and reduced spontaneous lung metastases.NBTXR3 intratumoral injection was feasible and safe. Preliminary signs of efficacy were observed in patients treated with NBTXR3/RT/anti-PD-1 including in patients refractory to anti-PD-1. Responses in distal, non-irradiated lesions were also observed in patients with resistance to anti-PD-1.ConclusionsWith demonstrated radioenhancement as well as immune system priming, NBTXR3 positions itself to be a paradigm shift catalyst in the treatment of cancers in a variety of clinical settings- definitive, palliative, and metastatic. These data support further development of NBTXR3 in combination with anti-PD-1 as well as other ICIs.Trial RegistrationNCT03589339