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Introduction: Diffuse large B-cell lymphomas (DLBCL) transformed from indolent B-cell non-Hodgkin lymphomas (B-NHL) or Richter transformation (RT) from chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL) are associated with a poor prognosis, particularly in patients (pts) with relapsed/refractory (RR) disease. PD-1/PD-L1 blockade has produced anti-tumor responses in pts with lymphoma; however, the response rate in pts with DLBCL is low. Preclinical data suggest that some "immunogenic" chemotherapies alter the tumor microenvironment and act synergistically with checkpoint blockade to improve anti-tumor responses. We evaluated the addition of the PD-L1 inhibitor, atezolizumab, to immunogenic chemoimmunotherapy, rituximab with gemcitabine and oxaliplatin (R-GEMOX) in pts with RR transformed DLBCL. Methods: Pts with DLBCL transformed from indolent B-NHL or RT from CLL that had received ≥ 1 prior regimen with ECOG performance status ≤ 2, and adequate organ and hematologic function were eligible for this phase 1 study. Two cohorts were enrolled, one for pts with DLBCL transformed from follicular lymphoma (FL) and another for pts with non-FL transformed DLBCL, including RT. R-GEMOX was administered without atezolizumab on C1D1, R-GEMOX+Atezo was given subsequently (Days 1+15 of 28 day cycles) for a maximum of 6 doses. Pts in CR could proceed to R+atezo q3w maintenance for up to 2 years. Pts could proceed to hematopoietic cell transplantation (HCT) without subsequent maintenance at the discretion of the treating MD. A safety lead-in (6 pts, any cohort) with dose-limiting toxicity (DLT) evaluation (28-day period, after 1 st dose of atezo) at dose level (DL) 1 (rituximab 375mg/m2, gemcitabine 1000mg/m2, oxaliplatin 100mg/m2, atezolizumab 840mg, with de-escalation dose level available) was enrolled to confirm the recommended phase 2 dose (RP2D). After confirmation of the RP2D, expansion will continue until enrollment of n=14 transformed FL and n=10 non-FL transformed DLBCL. Responses were assessed by investigators by PET-CT (after C2, C4, and then q12weeks) according to the 2014 Lugano Classification. The primary endpoint was safety and determination of the RP2D. Results: 23 pts were enrolled, 22 were evaluable for response and adverse events (AEs), 1 is too early. Baseline characteristics are summarized in Table 1. 1/6 pts had a DLT related to atezolizumab during safety lead-in: grade (G) 4 Stevens-Johnson syndrome leading to death. DL1 was the RP2D. 2 pts were replaced during safety lead-in due to progressive disease (PD) prior to completing DLT evaluation. The most common AEs with R-GEMOX+Atezo (n=22) were fatigue (50%), elevated transaminases (45%), thrombocytopenia (45%), nausea/vomiting (41%), diarrhea (32%), fever (32%), hypertension (HTN) (27%), and neutropenia (27%). Common G3-4 AEs included lymphopenia (n=4), neutropenia (n=4), HTN (n=3), leukopenia (n=3), thrombocytopenia (n=3). Among 7 pts who proceeded to maintenance R-atezo, the most common AEs were fatigue (n=4) and HTN (n=3). There were 2 deaths related to study therapy, the pt with SJS and 1 pt with infusion reaction leading to respiratory failure who also had PD with both factors likely contributing to death. In addition, 1 pt had both sepsis and PD and died during maintenance, considered possibly related to treatment. 7 deaths were unrelated to treatment, including 1 from complications after autologous HCT, and 6 after PD. 5 pts remain on treatment; 17 pts are off treatment. Reasons for study discontinuation include: insufficient response/PD (n=12), HCT (n=2), death due to toxicity (n=2), and G3 neuropathy during maintenance (n=1). Among the 22 pts, the ORR was 50% and CR rate was 29%. The 9 pts with transformed FL had an ORR of 67% and CR rate of 33%. The 13 pts with non-FL transformed DLBCL/RT had an ORR of 38% and CR rate of 23%. Of 9 pts with RT there was 1 CR and 1 PR while all 3 pts with transformed marginal zone lymphoma responded (2 CR, 1 PR). Among responders (n=11), the median duration of response was not reached (Figure 1). Of the 6 pts with CR, 2 proceeded to HCT, and 4 had ongoing CR lasting 30.7+ months (mo), 13.9+ mo, 6.8+ mo, 5.0+ mo. Of the 5 patients with PR, 1 pt died of SJS without PD, PR lasted 3 and 4 mo in 2 patients (PD), and 2 pts have ongoing response (0.5+ and 2.0+ mo). Conclusions: R-GemOx+Atezo was tolerable and produced objective responses in patients with transformed DLBCL/RT, with all pts in CR having ongoing response. Figure 1 Figure 1. Disclosures Herrera: Gilead Sciences: Research Funding; ADC Therapeutics: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Tubulis: Consultancy; Takeda: Consultancy; Merck: Consultancy, Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Kite, a Gilead Company: Research Funding; AstraZeneca: Consultancy, Research Funding; Karyopharm: Consultancy; Seagen: Consultancy, Research Funding. Allen: Epizyme: Consultancy; Kyowa Kirin: Consultancy; Secure Bio: Consultancy; ADC Therapeutics: Consultancy; MorphoSys: Consultancy. Popplewell: Hoffman La Roche: Other: Food; Novartis: Other: Travel; Pfizer: Other: Travel. Shouse: Beigene: Honoraria; Kite Pharma: Speakers Bureau. Siddiqi: AstraZeneca: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Oncternal: Research Funding; BeiGene: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Juno Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Kite Pharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen: Speakers Bureau; TG Therapeutics: Research Funding. Danilov: Gilead Sciences: Research Funding; Pharmacyclics: Consultancy, Honoraria; Beigene: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; TG Therapeutics: Consultancy, Research Funding; Takeda Oncology: Research Funding; Genentech: Consultancy, Honoraria, Research Funding; SecuraBio: Research Funding; Bayer Oncology: Consultancy, Honoraria, Research Funding; Astra Zeneca: Consultancy, Honoraria, Research Funding; Bristol-Meyers-Squibb: Honoraria, Research Funding; Rigel Pharm: Honoraria. Tuscano: Seattle Genetics: Research Funding; Bristol Myers Squibb: Research Funding; Takeda: Research Funding; Acrotech: Research Funding; Genentech: Research Funding; Pharmacyclics: Research Funding; Abbvie: Research Funding. OffLabel Disclosure: Atezolizumab is not approved for the treatment of aggressive B-cell non-Hodgkin lymphoma

The potential applications of nanomaterials in therapeutics are immense and to fully explore this potential, it is important to understand the interaction of nanoparticles with cellular components. To examine the interaction between nanoparticles and cell membrane receptors, this report describes the use of advanced fluorescence techniques to measure interactions between hydroxyapatite (HA) nanoparticles and epidermal growth factor receptors (EGFRs), as a model system. FITC-labelled HA nanoparticles and monomeric red fluorescent protein (mRFP)-conjugated EGFRs expressed in Chinese hamster ovary cells (CHO-K1) were generated and their interaction measured using acceptor photobleaching-fluorescence resonance energy transfer (AP-FRET) and fluorescence lifetime imaging microscopy-fluorescence resonance energy transfer (FLIM-FRET). Results confirmed that hydroxyapatite nanoparticles not only interacted with EGFR but also attenuated downstream EGFR signalling, possibly by hindering normal dimerization of EGFR. Furthermore, the extent of signal attenuation suggested correlation with specific surface area of the nanoparticles, whereby greater specific surface area resulted in greater downstream signal attenuation. This novel demonstration establishes fluorescence techniques as a viable method to study nanoparticle interactions with proteins such as cell surface receptors. The approach described herein can be extended to study interactions between any fluorescently labelled nanoparticle-biomolecule pair.

2538 Background: Patient variation in drug response and toxicity impacts all phases of drug development. While detailed sample-size calculations and analysis based on statistical methodology are critical for addressing variation in late stage trials, phase I studies pose unique and largely unsolved challenges related to variability. Changes in patient selection during the study, small sample-sizes and large patient variation in toxicity are exactly the kind of problems that statistical methods cannot address in small, isolated phase I studies, regardless of apparent mathematical rigor. We have documented these problems via a physician survey. Methods: A 10-question anonymous survey was sent to 670 oncologists at National Comprehensive Cancer Network (NCCN) and CCC institutions via an online survey. 19 % (126/670) of the oncologists polled responded. 78/126 (62%) specialized in Medical Oncology. The number of years in practice varied from 2-45 yrs with a median of 17 yrs. Results: a) 66% of all respondents stated that non-DLT toxicities on one dose level would impact their patient selection on the following dose level, conflicting with the assumption of random patient selection implicit in simulations used in evaluating statistical designs. b) Only 13% stated a desire to target a non-heme toxicity as high as 20% grade 3, while 87% desired a 10% or less grade 3 rate; c) More than half the respondents would prefer not to escalate if 3/3 patients experienced grade 2 LFTs; d) 82% of the respondents thought the appropriate target toxicity differed for patients depending on their potential for becoming a surgical candidate, furthering the need for personalized dosing. Conclusions: Statistical methods in phase I trials are unable to address many of the salient features of phase I study conduct and investigator goals. We will present several approaches we have initiated to address these limitations, and present future plans to help produce a more reliable estimate of a recommended dose. Supported in part by NCI grants U01CA062505, N01-CM-62209, and NCCN data collection assistance.