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PURPOSE The ATEMPT trial was designed to determine if treatment with trastuzumab emtansine (T-DM1) caused less toxicity than paclitaxel plus trastuzumab (TH) and yielded clinically acceptable invasive disease-free survival (iDFS) among patients with stage I human epidermal growth factor receptor 2–positive (HER2+) breast cancer (BC). METHODS Patients with stage I centrally confirmed HER2+ BC were randomly assigned 3:1 to T-DM1 or TH and received T-DM1 3.6 mg/kg IV every 3 weeks for 17 cycles or T 80 mg/m 2 IV with H once every week × 12 weeks (4 mg/kg load →2 mg/kg), followed by H × 39 weeks (6 mg/kg once every 3 weeks). The co-primary objectives were to compare the incidence of clinically relevant toxicities (CRTs) in patients treated with T-DM1 versus TH and to evaluate iDFS in patients receiving T-DM1. RESULTS The analysis population includes all 497 patients who initiated protocol therapy (383 T-DM1 and 114 TH). CRTs were experienced by 46% of patients on T-DM1 and 47% of patients on TH ( P = .83). The 3-year iDFS for T-DM1 was 97.8% (95% CI, 96.3 to 99.3), which rejected the null hypothesis ( P < .0001). Serially collected patient-reported outcomes indicated that patients treated with T-DM1 had less neuropathy and alopecia and better work productivity compared with patients on TH. CONCLUSION Among patients with stage I HER2+ BC, one year of adjuvant T-DM1 was associated with excellent 3-year iDFS, but was not associated with fewer CRT compared with TH.

TPS2657 Background: T-cell immunoreceptor with Ig and ITIM domains (TIGIT) is an inhibitory immune checkpoint receptor expressed on subsets of T cells and NK cells. SEA-TGT is an effector-function enhanced human mAb that targets TIGIT with pico-molar affinity and blocks TIGIT’s interaction with CD155 and CD112. SEA-TGT was developed to have amplified binding to and engagement of Fcγ receptors. Enhanced effector function increases TIGIT+ T-regulatory cell depletion, enhances innate immune cell activation, and augments naïve and memory CD8+ T-cell responses. Preclinically, SEA-TGT elicits superior anti-tumor immune responses compared to other TIGIT mAbs without effector-enhanced backbones, with curative anti-tumor activity as monotherapy and in combination with other immune-modulators. Methods: This phase 1, open-label, multicenter, dose-escalation/expansion study (NCT04254107) is assessing the safety, tolerability and preliminary activity of SEA-TGT monotherapy in up to 205 adults (≥18 years) with histologically or cytologically confirmed relapsed, refractory, or progressive metastatic solid tumors (non-small cell lung, gastric/GE junction carcinomas, cutaneous melanoma, head and neck squamous cell carcinoma, bladder cancer, ovarian cancer or triple-negative breast cancer) or lymphomas (classical Hodgkin lymphoma, diffuse large B-cell lymphoma, or peripheral T-cell lymphoma, not otherwise specified). SEA-TGT will be infused on Day 1 of 21-day cycles. In Part A, the safety and tolerability of SEA-TGT will be assessed in ̃25 subjects to identify the maximum tolerated dose and recommended phase II dose (RP2D). In Part B, the safety and antitumor activity of the RP2D will be assessed in ̃180 subjects in disease-specific expansion cohorts. Primary endpoints are adverse events, laboratory abnormalities, dose-limiting toxicities, and dose-level safety and activity. Secondary endpoints are objective response (OR) rates, duration of OR, complete response, progression-free survival, overall survival, PK, and antidrug antibodies. Exploratory biomarkers of SEA-TGT-mediated pharmacodynamic (PD) effects, PK-PD correlations, and correlative analyses of predictive and PD measurements with response, toxicity, and resistance will be explored. The study was opened April 2020 and is enrolling across sites in North America and Europe. Clinical trial information: NCT04254107.

e14537 Background: Over-expression of Bcl-2 family proteins is common in human cancers. Initial trials of the oral, pan-Bcl-2 inhibitor AT-101 showed acute dose limiting toxicity of Gr 3–4 AST/ALT (MTD 40 mg/d) and ileus with prolonged dosing daily (QD) for 21/28 days per cycle (Saleh, NCI/EORTC, 2005; James, ASCO, 2006 and Saleh, ASCO, 2007). MTD in the QD schedule has been previously reported. In this study different dosing schedules of AT-101 were tested in adults with advanced cancers and final results for the pulse dosing schedule of twice a day for three days every other week (b.i.d. x 3d EOW) are being reported. Methods: Serial patient (pt) cohorts received AT-101 at escalating doses of 30–80 mg b.i.d. x 3d EOW. Adverse events (AEs) were graded by the NCI CTCAE v3.0. Efficacy was determined by RECIST. Results: 37 pts have been enrolled. Safety data is available on 34/37 pts. In this b.i.d. x 3d EOW dosing schedule, ileus/small bowel obstruction (SBO) occurred in 3 pts (one at each dose level of 30, 40 and 50 mg) and was the dose limiting toxicity for this schedule. Of note, the SBO that occurred at 30 mg was felt to be unrelated to study agent therefore, 30 mg b.i.d. x 3d EOW was the MTD determined for this schedule. The most common (>50%) grade 1–2 AEs included: nausea, vomiting, diarrhea, fatigue and anorexia. Grade 3–4 AEs occurring in > 2 pts include: nausea, abdominal pain, elevated AST (3 pts each), vomiting, fatigue, dehydration (4 pts each), hypokalemia (5 pts). Stable disease was reported in 13/37 (35%) pts. One pt with NSCLC continues on study with stable disease for 33 cycles and 2 additional pts were on study with stable disease for 18 and 9 cycles. The mean Plasma Cmax was 301 ng/ml (+ 477 ng/ml SD) and mean AUC for 30 mg b.i.d.x3d EOW was 1080 ng*hr/ml (+ 1990 ng/ml SD) with a median peak concentration at 4 hours post dose. Conclusions: Pulse dosing of AT-101 achieved an MTD of 30mg b.i.d. x 3d EOW and is associated with reduced toxicity than continuous daily dosing, and may be preferable in combination regimens. [Table: see text]

Abstract In relapsed/refractory Hodgkin lymphoma (R/R HL), immunotherapies such as the anti-programmed death-1 inhibitor pembrolizumab have demonstrated efficacy as monotherapy and are playing an increasingly prominent role in treatment. The CD30/CD16A-bispecific antibody AFM13 is an innate immune cell engager, a first-in-class, tetravalent antibody, designed to create a bridge between CD30 on HL cells and the CD16A receptor on natural killer cells and macrophages, to induce tumor cell killing. Early studies of AFM13 have demonstrated signs of efficacy as monotherapy for patients with R/R HL and the combination of AFM13 with pembrolizumab represents a rational new treatment modality. Here, we describe a phase 1b, dose-escalation study to assess the safety and preliminary efficacy of AFM13 in combination with pembrolizumab in patients with R/R HL. The primary objective was estimating the maximum tolerated dose; the secondary objectives were to assess safety, tolerability, antitumor efficacy, pharmacokinetics, and pharmacodynamics. In this heavily pretreated patient population, treatment with the combination of AFM13 and pembrolizumab was generally well tolerated, with similar safety profiles compared to the known profiles of each agent alone. The combination of AFM13 with pembrolizumab demonstrated an objective response rate of 88% at the highest treatment dose, with an 83% overall response rate for the overall population. Pharmacokinetic assessment of AFM13 in the combination setting revealed a half-life of up to 20.6 hours. This proof-of-concept study holds promise as a novel immunotherapy combination worthy of further investigation. This phase 1b study was registered at www.clinicaltrials.gov as NCT02665650.

1011 Background: Several trials have shown 25-30% pathologic complete response (pCR) rates in patients with HER2+ BC treated with LT therapy (+ endocrine therapy if ER+), but no chemotherapy (CTX). We hypothesize that a multiparameter classifier, comprised of HER2 gene and protein levels, intratumor heterogeneity (ITH), HER2-enriched (E) subtype, and PIK3CA mutation status can identify patients whose tumors are “addicted” to HER2 signaling and are likely to achieve pCR from a CTX-sparing de-escalation strategy. Methods: Baseline specimens from 2 trials (TBCRC023 [NCT00999804] and PAMELA [NCT01973660]) of neoadjuvant CTX-sparing LT (+ endocrine therapy if ER+) in HER2+ BC were used. HER2 protein and ITH (scored for % 3+ by IHC), and gene amplification (HER2:CEP17 ratio and copy number (CN) by CISH) were measured on the same slide by the dual gene protein assay (GPA). HER2-E and PIK3CA mutation status were assessed by research-based PAM50 and MSK-IMPACT platforms, respectively. A decision tree algorithm was used to determine the GPA cutoffs and to construct the classifier of response (by pCR) in TBCRC023, which was then validated in PAMELA. Results: Of the evaluable patients from TBCRC023 (N = 130) and PAMELA (N = 151), GPA data were available for 121 and 94 cases, respectively. Both cohorts exhibited similar distributions for HER2 ratio, CN, and % 3+, and a strong correlation between HER2 ratio and CN (R > 0.92). In TBCRC023, 73 cases had data from GPA, PAM50, and IMPACT, of which 15 had pCR. Recursive partitioning identified cutoffs of HER2 ratio > 4.6 and % 3+ > 97.5% in both the GPA data cohort (N = 121) and complete data cohort (N = 73). With PAM50 and IMPACT data, the model added HER2-E and PIK3CA wild-type (wt). For practical reasons, the classifier was locked as HER2 ratio ≥ 4.5 AND % 3+ ≥ 90% AND PIK3CA-wt AND HER2-E, which yielded a PPV of 55% and NPV of 94%. Validation in PAMELA using 45 cases with data for all 3 assays yielded PPV of 44% and NPV of 82%. 29 TBCRC023 cases without IMPACT data could be predicted to be non-pCR, of which 26 were correct (NPV = 89%). In PAMELA, 66 additional cases could be predicted to be non-pCR, of which 54 were correct (NPV = 81%). Conclusions: We have constructed a multiparameter classifier that can predict pCR with targeted therapy alone that compare to pCR rates of CTX + dual anti-HER2 in unselected patients. Prospective validation in a clinical trial is warranted. [Table: see text]

Abstract Rationale Escalation of the Zevalin dose is limited by hematologic toxicity associated with marrow B-cells ± tumor cells. Rituxan treatment before Zevalin may reverse marrow infiltration with malignant and normal B-cells allowing an increase in the dosage of Zevalin with enhanced radiation delivery to lymphoma tumor sites. Since NHL is radiation sensitive, a substantial increase in radiation dose delivered should increase the ORR and CR rates. Design Low-grade follicular/transformed NHL patients receive 4 weekly dose of Rituxan (375mg/m2) before the corresponding Zevalin dose. Bilateral bone marrow biopsies/aspirates as well as biodistribution and dosimetry studies using 111In-2B8 were obtained before and after Rituxan. The trial was schedule to escalate the Zevalin dose (from 0.4 to 0.7 mCi/Kg). After completion of the 0.4 mCi/kg cohort an additional cohort of Rituxan sensitive patients using 0.3 mCi/kg was completed. Safety, pharmacokinetics, dosimetry and preliminary responses are presented. Results 5 pts were enrolled in the 0.4mCi/kg cohort and 6 pts in the 0.3 mCi/kg cohort. In the 10 Rituxan sensitive patients the plasma T ½ and the AUC of 111In-2B8 increased after the administration of Rituxan, with a reduction in the plasma clearance (T½ from 45 ± 4.5 hours to 54 ± 1.9 hours, AUC from 60 ± 10 hrs/μCi/ml to 85 ± 14 hrs/μCi/ml, and the clearance from 1.4 ± 0.3 ml/hrs/kg to 0.9 ± 0.2 ml/hrs/kg). Dosimetry showed no differences in the radiation-absorbed dose for major normal organs (whole body, liver, kidneys) except for the spleen in which a reduction was observed in 7 out of 10 patients. The radiation-absorbed dose to the marrow increased after Rituxan; from 3.6 rads/mCi to 4.28 rads/mCi. In the 0.4 mCi/kg cohort 3 out of 4 evaluable patients for response had a complete response, and 1 patient had progression documented at initial evaluation six weeks post-Zevalin (patient refractory to previous Rituxan). No non-hematological toxicity was observed. One patient had a grade 4 thrombocytopenia, 3 patients had grade 3 thrombocytopenia, and 4 patients had grade 4 WBC and ANC. All patients recovered within two weeks after the nadir. Two out of 6 patients treated in the 0.3 mCi/kg cohort had complete response by physical evaluation, and 4 had partial response; no early progressions were seen in this cohort. No non-hematological toxicity was observed. Only one patient had a grade 4 WBC and ANC, and 2 patients had a grade 3; 3 patients had grade 3 thrombocytopenia; all patients recovered. Conclusions The administration of high doses of Rituxan before Zevalin prolongs the circulation time of the radiolabeled antibody and increases the bone marrow exposure to the radioisotope. Additionally, the increased amount of the radiolabeled antibody available after Rituxan therapy with the prolonged circulation time may explain the unusual high complete response rate observed in this small number of patients despite extensive chemotherapy failures. Although this is very provocative data, the number of patients is very limited to generate a strong conclusion. The trial continues at this time.

Abstract BACKGROUND: SGN-40 is a humanized monoclonal antibody that targets CD40. Upon binding to CD40, SGN-40 triggers pro-apoptotic signal transduction pathways and mediates effector cell functions (ADCC and ADCP). SGN-40 demonstrated preliminary anti-tumor activity in a phase 1 study of non-Hodgkin lymphoma, including diffuse large B-cell lymphoma (DLBCL) patients (ASH 2006, Abstract 695). METHODS: We conducted a multicenter, phase 2, open-label study to determine the overall response rate and toxicity profile of SGN-40 in patients with relapsed DLBCL. Tumor samples were assessed by a central lab for pathology confirmation and CD40 expression. Eligible patients had de novo or transformed DLBCL at diagnosis and were excluded if previously treated for indolent lymphoma. Required prior therapy consisted of combination chemotherapy with rituximab and, if eligible, autologous stem cell transplantation. Patients received 6 intravenous infusions of SGN-40 over 5 weeks (Cycle 1) with intra-patient dose loading (1 mg/kg on Day 1; 2 mg/kg on Day 4; 4 mg/kg on Day 8) and 8 mg/kg/wk thereafter. Responding patients and those with stable disease were eligible to continue therapy until disease progression or a maximum of 12 cycles. RESULTS: Forty-six patients (28 M, 18 F), with a median age of 72 years (range 17–85), were enrolled at 10 centers in the US. Patients were heavily pre-treated, with a median of 4 prior systemic chemotherapy regimens (range 1–10). Immunohistochemistry analysis of patient tumor samples demonstrated high expression of CD40 in all patients with the exception of 1 patient who was negative. Thirty-eight of the 46 patients met predefined criteria for evaluation (completed dose loading and had no major protocol violations). Best responses seen were CR (n=2, 5%) and PR (n=2, 5%), yielding an ORR of 10%. Furthermore, 9 (24%) patients had SD as best response. Reductions in tumor size were seen in approximately one-third of patients. Twenty (53%) patients had PD and 5 (13%) patients have yet to be assessed. Treatment with SGN-40 was generally well tolerated. Grade 3/4 events that occurred in more than 1 patient in the intent-to-treat population (N=46), regardless of drug attribution were thrombocytopenia (n=5); neutropenia (n=4); and anemia, fatigue, pneumonia, hyponatremia, DVT, and disease progression (n=2 pts each). Of these events, only fatigue (n=2) and neutropenia (n=2) were considered drug related by the investigator. CONCLUSION: Monotherapy with SGN-40 in DLBCL patients is well tolerated and resulted in objective responses consistent with the previous phase 1 experience. These data support further evaluation of SGN-40 in combination with chemotherapy in non-Hodgkin lymphoma; 3 combination clinical trials are ongoing. Retrospective correlation of clinical outcome and a gene signature that includes baseline CD40 activation status are planned.

1052 Background: TIG, an agonistic anti-DR5 monoclonal antibody, triggers apoptosis in DR5+ human tumor cells without the aid of crosslinking. TIG has shown strong in vitro and in vivo activity against basal-like breast cancer cells that is enhanced by chemotherapy like paclitaxel. Methods: Randomized 2:1 phase II trial of nab-PAC with/without TIG in TNBC patients. Patients stratified by prior exposure to chemotherapy in the metastatic setting. Patients received nab-PAC weekly x 3 and TIG every other week, every 28 days. Primary endpoint was overall response rate (ORR). Secondary objectives were safety, progression free survival (PFS), TIG immunogenicity, and PK. Biopsies and circulating tumor cells were collected. The trial was not powered to compare arms but allowed early stopping for futility and was sized to estimate ORR with 95% CI. Results: 64 patients enrolled, 60 treated; 39 in the combination arm and 21 in the nab-PAC arm. Of the 39 in the combination arm, there were 2 CR, 9 PR (1 near CR, 96% tumor reduction), 11 SD and 17 PD; ORR 28% (95% CI 14%-42%). Of the 21 in the single agent arm, there were no CR, 8 PR, 4 SD and 9 PD; ORR 38% (95% CI 17%-59%). Higher ORRs were seen in the chemotherapy naïve patients (58% vs. 15% combination and 42% vs. 35% single agent). 2 patients with CR, 1 near CR, and 1 PR in the combination arm are still on therapy (602+, 531+, 466+, 460+ days). PFS was similar in both groups (3.6 months); higher in chemotherapy naïve patients. Combination was well tolerated (most toxicities grade 1/2); the most common AEs were fatigue, alopecia, peripheral sensory neuropathy, anemia, neutropenia, nausea, thrombocytopenia, anorexia, diarrhea, and vomiting. No grade 4 or 5 toxicity. No apparent added toxicity with TIG was seen. Conclusions: Combination therapy with nab-PAC + TIG was well tolerated, without apparent improvement in ORR relative to nab-PAC alone; however, 4 subjects treated as first-line had prolonged clinical benefit with the combination, and correlative studies will investigate markers that might predict clinical outcome (Next-Gen genomic analysis). Clinical trial information: F101004001.