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2639 Background: In situ immunization involves intratumoral (IT) injection of immunostimulatory agents to modify the tumor microenvironment with the goal of inducing an anti-tumor T cell response. Here, we report preliminary results of a clinical trial exploring in situ immunization with a virus like particle (VLP) combined with systemic pembrolizumab (Pembro) in lymphoma. The VLP, known as CMP-001 or vidutolimod (Vidu), is composed of the bacteriophage Qb capsid encapsulating the TLR9 agonist G10. Preclinical studies demonstrated generation of antibodies against the Qb capsid (anti-Qb) is necessary for Vidu to induce an anti-tumor response. In other cancers, early phase clinical trials of in situ immunization with Vidu, with and without systemic anti-PD1 therapy, have revealed early promising results. Methods: This trial included patients with relapsed lymphoma that have failed at least 1 line of therapy. The first dose of Vidu is given subcutaneously to stimulate anti-Qb that opsonizes the VLP. This is followed by IT Vidu administered weekly for seven doses, then at 3-week intervals. Pembro (200 mg fixed dose) is given intravenously every 3 weeks. Subjects continue treatment if they do not experience unacceptable toxicities and in the investigator’s opinion continued treatment is in the subject’s best interest. Fine needle aspirates for flow cytometric analysis are obtained prior to therapy and 4-6 weeks following initiation of therapy. Results: Six patients have enrolled to date (1 CR, 2 PR, 1 SD, 2 PD). The first 3 patients received 5mg Vidu per dose and the second cohort 7.5 mg per dose. Common side effects included chills, rigors, mild headache, and fatigue. These typically resolved within 4 hours after receiving the injection. Conclusions: In situ immunization with Vidu plus systemic anti-PD1 is a promising therapy in lymphoma. The ability to generate anti-Qb that opsonizes the VLP appears to be necessary for Vidu to induce an immune and therapeutic response. Accrual and correlative studies are continuing with the modification that generation of functional-Qb after the first dose of Vidu is required before patients receive IT therapy. Clinical trial information: NCT03983668. [Table: see text]

Venous thromboembolic events (VTE) are common after the diagnosis of lymphoma. Although various risk factors have been associated with VTE in cancer patients, there is no specific VTE risk prediction score for diffuse large B cell lymphoma (DLBCL) patients. The Khorana score is a prediction-model of VTE in cancer patients receiving chemotherapy that incorporates clinical and laboratory parameters. We evaluated the risk factors for VTE, the effect of VTE on the outcomes of DLBCL patients and the utility of the Khorana score in DLBCL patients. Methods: We searched the Hematologic Malignancies Database of University Hospitals Seidman Cancer Center for newly diagnosed DLBCL patients between 2002 and 2014. Data on patient characteristics including risk factors, disease characteristics, treatment, outcomes and VTE was collected. The Khorana score was calculated using clinical (disease type, body mass index) and laboratory (hemoglobin level, platelet and leukocyte count) parameters. Risk factors identified as having statistical significance on univariate Cox proportional hazards analysis (p Results: Four hundred DLBCL patients were included for analysis. Median age at diagnosis was 63 with 235 patients above the age of 60. Two hundred and thirty seven patients (59.3 %) had advanced stage at diagnosis and 14 patients (3.5%) had a prior history of VTE. Baseline characteristics are listed in Table 1. Sixty percent of patients had a Khorana score of 1 with no risk factors in addition to the diagnosis of lymphoma. At median follow up of 33 months, 70 patients (18%) presented a VTE, with 1-year and 3-year cumulative incidence of 10.1% (95% CI 7.1-13.6) and 14% (95 % CI 10.8-18), respectively. Fifty-seven VTE (81% of all VTEs) were diagnosed in patients with active disease (at diagnosis, relapse or during active therapy). The Khorana score separated DLBCL patients in three VTE risk groups: intermediate (1 point), high (2 points) and very high (3 or more points) with 1 year cumulative incidence of VTE of 6.4%, 11.6% and 22.2%, respectively (p = 0.009) (Figure 1). On univariate analysis, bone involvement by lymphoma, elevated corrected calcium (>12g/dL), increased white cell count (>11,000/mcl), hemoglobin (800/mcl) and chromosomal translocations involving MYC presented statistically significant increases in hazard of VTE (Table 2). On multivariate analysis only bone involvement (p=0.017) and anemia (p=0.035) retained statistical significance as risk factors for VTE. Three-year OS for patients presenting with VTE within 1 year of DLBCL diagnosis was 46.7 % (95% CI 30-63.3) vs. 72.3% (95% CI 67.4-77.3) in subjects without early VTE (p=0.05) (Figure 2). Presence of VTE at any time after DLBCL diagnosis was also associated with worse OS rates, with estimated 3-year OS of 52.2 % (95 % CI 39.8-64.7) for subjects experiencing VTE and 74 % (95 % CI 69-79) for those without VTE after DLBCL diagnosis (p Conclusion: Venous thromboembolic events are common after diagnosis of DLBCL and are associated with worsened outcomes. The Khorana score is capable of identifying patient subgroups with increased risk of VTE. Additional parameters associated with aggressive disease and advanced stages could further help in VTE risk stratification for selection of patients who may benefit from antithrombotic prophylaxis. Prospective validation of VTE risk assessments and clinical trials of VTE prevention are needed in this high=risk population. Disclosures Caimi: Gilead: Consultancy; Novartis: Consultancy; Genentech: Speakers Bureau; Roche: Research Funding.