Intratumoral G100 to Induce Systemic Immune Responses and Abscopal Tumor Regression in Patients with Follicular Lymphoma.

7537 Background: Follicular lymphoma (FL) is an incurable malignancy with patients (pts) ultimately relapsing following standard therapies. Active immunotherapy has the potential to induce life-long host anti-tumor immunity and disease control. G100 consists of glucopyranosyl lipid-A (GLA), a TLR-4 agonist in a specific formulation. Preclinically, G100 activates dendritic cells, T cells and NK cells, and triggers systemic anti-tumor immunity. In Merkel Cell carcinoma pts, G100 administered intratumorally (IT) induced tumor inflammation and responses including a CR after G100 alone. This is the first study of G100 IT in pts with NHL. Methods: Previously treated or naïve pts with FL with an injectable tumor site and distal sites of disease were eligible. In Part 1, G100 cohorts of 5 or 10µg were enrolled in a 3+3 design, followed by a large tumor ( > 4cm) cohort at 20µg. Pts received 6-9 doses of G100 IT ~qwk after radiation (RT, 2 Gy x2 doses) to the lesion. A 2nd course of G100 could be given without RT to an additional site. Results: As of 31Dec16, all 9 pts in Part 1 dose escalation (3 pts each at 5, 10, or 20 µg/dose) were evaluable for safety and efficacy. An additional 13 pts at 10µg/dose were included in the safety analysis only. No G100-related DLTs or SAEs were observed at any dose level. Of 22 safety pts, all G100 related AEs were grade 1/2 and none occurred in > 2 pts. Tumor biopsies following G100 demonstrated diffuse infiltration of CD8+ T cells in 5/5 pts and T cell repertoire analyses indicated an increased frequency of clonal tumor infiltrating lymphocytes (TILs). Best responses include: 4 PRs (45%), 3 SDs (33%) and 2 pending (22%). Of the 4 PR pts, tumor regression ranged 58-89% including up to 56% shrinkage of abscopal (distal) sites. Conclusions: G100 IT was safe, well-tolerated, induced CD8+ T cell infiltration and expansion of TIL clones. G100/RT treated and abscopal lesion regressions were observed signifying the induction or boosting of systemic anti-tumor immunity. The induction of immune responses, favorable safety profile and clinical activity indicate that G100 IT is an active agent that warrants further investigation. Part 2 enrollment continues with randomization to G100/RT ± pembrolizumab. Clinical trial information: NCT02501473.