(50%), with an overall disease control rate of 61.5%. AFM13 was also active in brentuximab vedotin-refractory patients. In 13 patients who received doses of ‡1.5 mg/kg AFM13, the overall response rate was 23% and the disease control rate was 77%. AFM13 treatment resulted in a significant NK-cell activation and a decrease of soluble CD30 in peripheral blood. In conclusion, AFM13 represents a welltolerated, safe, and active targeted immunotherapy of Hodgkin lymphoma. A phase 2 study is currently planned to optimize the dosing schedule in order to further improve the therapeutic efficacy. This phase 1 study was registered at www.clinicaltrials.gov as #NCT01221571. (Blood. 2015;125(26):4024-4031)

We conclude that Mab was not effective in achieving primary efficacy as assessed by neutralization of circulating HBsAg. Whether a combination of Mab with an antiviral agent that reduces the HBsAg load--and therefore minimizes the risk of adverse events--may result in clinical efficacy should be investigated.

Despite the several advances in the last few years into treatment of advanced lung cancer, the 5-year survival remains extremely low. New therapeutic strategies are currently under investigation, and immunotherapy seems to offer a promising treatment alternative. In the last decade, therapeutic cancer vaccines in lung cancer have been rather disappointing, mainly due to the lack of efficient predictive biomarkers. A better refinement of the patient population that might respond to treatment might finally lead to a success story. For the first time, the immune checkpoint inhibitors are demonstrating sustained antitumor response and improved survival and they may be the first immunotherapeutics available for patients with lung cancer.

Introduction: AFM13 is a CD30/CD16A bispecific tetravalent TandAb antibody that recruits and activates NK-cells by specific binding to CD16A for targeted lysis of CD30+ tumor cells. Given promising clinical activity and safety profile of AFM13 and proof-of-mechanism demonstrating dependence on the immune response, potential synergy of AFM13 and checkpoint modulators was evaluated. Methods: Efficacy of AFM13 alone or in combination with anti-CTLA-4, anti-PD-1, or anti-CD137 antibodies was assessed by in vitro cytotoxicity assays with human PBMCs or enriched NK-cells and CD30+ target cells as well as patient-derived xenograft in vivo models with autologous PBMC. To evaluate NK-cell-mediated lysis of CD30+ lymphoma cell lines, 4 hour cytotoxicity assays were performed with PBMCs or enriched NK-cells as effector cells in the presence of suboptimal concentrations of AFM13 alone, and in combination with anti-CTLA-4, anti-PD-1, or anti-CD137 antibodies. For the in vivo model tumor fragments derived from surgical specimens of newly diagnosed patients with CD30+ Hodgkin Lymphoma were xenografted (PDX) in immuno-deficient mice. After 28 days mice were reconstituted with autologous patient-derived PBMC and treated with AFM13 alone and in combination with anti-CTLA-4, anti-PD-1, or anti-CD137 antibodies weekly for a total of three weeks. Tumor size, tumor-infiltrating human lymphocytes and intra-tumoral cytokines were evaluated on day 58. Results: AFM13 as a single agent at suboptimal concentrations induced effector-to-target cell-dependent lysis of CD30+ lymphoma cells up to 40% using enriched NK-cells as effector cells in a 4 hour in vitro assay. Immune-modulating antibodies alone mediated substantially lower lysis (<25%). However, the addition of anti-PD-1 or anti-CD137 to AFM13 strongly enhanced specific lysis up to 70%, whereas the addition of anti-CTLA-4 to AFM13 showed no beneficial effect. The most impressive increase of efficacy was observed when AFM13 was applied together with a combination of anti-PD-1 and anti-CD137. In vivo, reduction of tumor growth was observed when AFM13 and anti-PD-1 were used as single agents or when AFM13 was combined with anti-CD137. Synergy was most impressive in these PDX models for the combination of AFM13 and anti-PD-1 which led to a very strong reduction of tumor size. Of note, reduction of tumor growth was strongly correlated with infiltrating NK- and T-cells and intra-tumoral cytokines. Conclusions: The combination trials performed with companion intra-tumoral assessment of lymphocytes and cytokines may enhance the efficacy of AFM13 in patients. This may be explained by a potential cross-talk between NK-cells and T-cell which was enhanced when AFM13 was used in combination with checkpoint modulators. Disclosures No relevant conflicts of interest to declare.

3067 Background: PCNA is a conserved scaffold protein orchestrating DNA replication, repair or bypass pathways as well as cellular signaling and apoptosis. More than 500 protein-PCNA interactions have been identified which are mediated via two binding motifs, the PIP-box and APIM. Cellular stress, to which cancer cells and cells of tumor microenvironment are exposed, increases the affinity of the APIM motif. APIM-containing proteins bind to PCNA and mediate processes of escape mechanisms and survival of cancer cells. ATX-101 is a cell penetrating peptide containing APIM. It inhibits protein binding via APIM, resulting in cancer cell death and altered cellular signaling. Anticancer effects of ATX-101 have been demonstrated in vitro and in vivo. Methods: A FIH study using a 3+3 dose escalation design was conducted. Patients with late-stage solid tumors received weekly infusions of 20, 30, 45 and 60 mg/m² over 6 weeks. Primary objective was safety, secondary objectives were PK and efficacy. Patients with stable disease (SD) after 6 weeks could continue treatment in a long-term follow-up (LTFU) study. Results: As of January 2021, 22 patients have been treated. All patients received in average 3.8 [1-9] prior treatment lines, all but one had progressive disease at study entry and 80% were refractory to the last therapy. No dose limiting toxicity or death and no treatment related Grade 3/4 or serious adverse events were reported. The maximum tolerated dose was not reached. Mild to moderate infusion related reactions (IRR) were observed in 73% of patients. They were not dose dependent and resolved completely after treatment interruption and/or symptomatic treatment. IRRs occurred despite premedication and could cause infusion interruptions with extended infusion duration. Experiments in dogs indicate that transiently increased histamine levels may cause IRRs. However, elevated histamine and tryptase levels could not be measured in patients so far. ATX-101 exposure was dose-dependent. Cmax was reached either at the middle or at the end of infusion. ATX-101 disappeared quickly from plasma and was not detectable 5 - 60 minutes post infusion. 13 patients finished the FIH study, 10 had SD after 6 weeks. 9 of 10 patients moved into the LTFU study. The treatment duration in the LTFU study varied from 2.1 to 15.6 months (median 4.2 months). Conclusions: ATX-101 is well tolerated at all dose levels with IRRs being the most frequent AEs. Drug exposure is dose dependent with rapid plasma clearance, which confirms in vivo data demonstrating the quick uptake by cells of all organs. The observed duration of SD may be attributed to ATX-101 activity. Proof of concept combination studies are being initiated. Clinical trial information: 375262.