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9060 Background: Dual blockade of PD-1 and CTLA-4 has shown improved overall survival (OS) in combination with a short course of chemotherapy. KN046 is a novel bispecific antibody that blocks both PD-L1 interaction with PD-1/CD80 and CTLA-4 interaction with CD80/CD86. We hypothesized that KN046 could be combined with a full course of chemotherapy and build more durable clinical benefit. Methods: This study enrolled systemic treatment naive, stage IV NSCLC patients (pts). Eligible pts received KN046 plus platinum doublet chemotherapy until progressive disease, unacceptable toxicity, withdrawal of informed consent or death. Efficacy evaluation was performed by investigators per RECIST 1.1. Safety and tolerability were assessed per NCI-CTCAE v5.0. Results: As of the Jan. 19, 2021, 87 pts [Cohort 1 (n = 51), Cohort 2 (n = 36)] have been enrolled with 83 pts having tumor PD-L1 expression data (PD-L1 ≥1%: 55.4%; PD-L1 < 1%: 44.6%). 33.3% pts remained on the study treatment and 66.7% pts discontinued treatment due to disease progression (27.6%), TEAE (13.8%), death (9.2%) and other reasons (16%). The median treatment duration of KN046 was 21 weeks (range: 1.6̃68.7 weeks). Treatment related TEAE (TRAE) occurred in 92% pts. 25.3% pts experienced Grade≥3 TRAE [diarrhoea (5.7%), alanine aminotransferase increased (4.6%), infusion related reaction (3.4%), rash (3.4%), aspartate aminotransferase increased, dermatitis allergic and immune-mediated pneumonitis (2.3%, respectively), anaphylactoid reaction, autoimmune hepatitis, back pain, bilirubin conjugated increased, hypertension, neutrophil count decreased, platelet count decreased, pneumonitis, rash maculo-papular, septic shock and white blood cell count decreased (1.1%, respectively). In 81 efficacy evaluable pts, the overall objective response rate (ORR) was 50.6% (95% CI: 39.3%,61.9%) and disease control rate (DCR) was 87.7% (95% CI: 78.5%-93.9%). The ORR and DCR in pts with non-squamous NSCLC (n = 48) were 45.8% (95% CI: 31.4%, 60.8%) and 89.6% (95% CI: 77.3%, 96.5%). The ORR and DCR in pts with squamous NSCLC (n = 33) were 57.6% (95% CI: 39.2%, 74.5%) and 84.8% (95% CI: 68.1%, 94.9). Progression free survival (PFS) and OS events have occurred in 53% and 18% patients. Median PFS was 5.9 (95%CI: 5.3, 8.7) months. Median OS was not reached. OS rate at 12 and 15 months were both 74.9%. Similar OS curves have been observed in PD-L1 ≥1% and PD-L1 < 1% pts. In PD-L1 ≥1% patients, median PFS was 6.7 months (10.8 months for PD-L1 ≥1% squamous NSCLC pts). Conclusions: KN046 combined with platinum doublet chemotherapy is tolerated and has shown promising clinical benefit as IL treatment for stage IV NSCLC particularly in PD-L1≥1% tumors and squamous histology. Pivotal Phase III trial in advanced unresectable or metastatic squamous NSCLC is currently ongoing. Clinical trial information: NCT04054531.

510 Background: Trastuzumab (T) increases the incidence of cardiac events (CEs) in patients (pts) with early breast cancer (BC). Dual blockade with P+T improves BC outcomes and is the standard of care for high-risk HER2-positive BC pts following the phase 3 APHINITY trial that evaluated the addition of P or placebo (Pla) to T and chemotherapy (CT). We analyzed the cardiac safety of P+T in APHINITY. Methods: APHINITY eligibility required a left ventricular ejection fraction (LVEF) ≥55% at study entry. LVEF assessment was performed every 3 months (mos) during treatment, every 6 mos up to month 36, and yearly thereafter. Primary CE was defined as heart failure (HF) class III/IV and a significant decrease in LVEF of at least 10 percentage points from baseline and to

212 Background: Dual blockade of immune checkpoint molecules, PD-1 and LAG-3, has been proposed to restore T-cell function and thus enhance antitumor responses. This Phase I trial evaluated BI 754091 (anti-PD-1) with BI 754111 (anti-LAG-3) antibodies in Asian pts with advanced solid tumors (NCT03433898). Here, we present results from pts with anti-PD-(L)1 inhibitor-naïve gastric/gastroesophageal junction or esophageal cancer (Cohorts A and B). Methods: In Parts 1 and 2 (dose escalation), the recommended dose for the combination was determined as BI 754091 240 mg + BI 754111 600 mg IV Q3W. In Part 3, the combination was assessed in expansion cohorts including pts with gastric/gastroesophageal junction cancer (Cohort A) and esophageal cancer (Cohort B). Eligible pts had received ≥1 line of prior systemic therapy but no prior anti-PD-(L)1 therapy. The primary endpoint in Part 3 was objective response (OR; confirmed complete response or partial response [PR]) per RECIST 1.1. Results: In Cohort A/B, 36/37 pts were treated:26/31 (72/84%) male, median age 60/63 years. Patients were enrolled in Taiwan (1/7 pts, 3/19%), Japan (12/27 pts, 33/73%) or Korea (23/3 pts, 64/8%). The median number of regimens of prior systemic therapy was 2/2 (Cohorts A/B, range: 1–6/1–4). All pts in Cohort B had squamous cell carcinoma. At the time of analysis, pts in Cohort A/B had undergone a median of 84/73 days on treatment (range: 31–346/8–325), from the start of treatment until the date of snapshot, death or discontinuation. Confirmed OR (PR) was observed in 4/7 pts in Cohorts A/B; overall response rate (ORR) was 11% and 19%. Stable disease (SD) was observed in 10/8 (28/22%) pts in Cohorts A/B and overall disease control rate was 39/41%. In Cohorts A/B, adverse events (AEs) and treatment-related AEs were experienced by 30/34 (83/92%) and 12/22 (33/59%) pts, respectively. The most commonly reported AEs were pyrexia (25/19%), decreased appetite (17/19%), increased aspartate aminotransferase (11/14%), anemia (11/11%) and nausea (6/14%). In Cohort A/B, 9/15 (25/41%) pts experienced immune-related AEs, most commonly rash in Cohort A (4 pts; 11%) and hyperthyroidism in Cohort B (4 pts; 11%). In Cohorts A/B, 2/6 (6/16%) patients experienced AEs leading to discontinuation of treatment. Conclusions: Treatment was well tolerated and preliminary antitumor activity was seen. Addition of LAG3 did not improve ORR beyond that expected for an anti-PD-1 monotherapy in gastric and esophageal cancer without patient selection. Clinical trial information: NCT03433898. [Table: see text]

3054 Background: Dual blockade of immune checkpoint molecules, PD-1 and LAG-3, may enhance the anti-tumor response versus PD-1 blockade alone. This Phase I trial investigated BI 754091, an anti-PD-1 antibody, as monotherapy and in combination with BI 754111, an anti-LAG-3 antibody, in Asian pts with advanced solid tumors. Methods: This trial comprised 3 parts. Parts 1 and 2 (dose escalation) were in pts with unresectable/metastatic solid tumors. In Part 1, pts received BI 754091 240 mg intravenously (iv), every 3 weeks (q3w); in Part 2, pts received BI 754091 240 mg in combination with BI 754111 (400 mg, 600 mg or 800 mg iv, q3w). Dose escalation was guided by a Bayesian logistic regression model, with overdose control. The primary endpoint in Parts 1 and 2 was maximum tolerated dose (MTD) of BI 754091 alone or in combination with BI 754111, based on dose-limiting toxicities (DLTs) in Cycle 1. In Part 3, BI 754091 240 mg plus BI 754111 600 mg q3w was assessed in 4 expansion cohorts. Cohorts A–C included pts with: A) gastric/esophagogastric junction cancer; B) esophageal cancer; C) hepatocellular cancer; all had received ≥1 line of prior systemic therapy and no prior anti-PD-(L)1 therapy. Cohort D included pts who had received prior anti-PD-(L)1 therapy for the tumor types in Cohorts A–C. The primary endpoint in Part 3 was objective response (confirmed complete response or partial response [PR] per RECIST 1.1). Results: In Part 1, 6 pts received BI 754091 240 mg. In Part 2, 9 pts received BI 754091 240 mg plus BI 754111 (400 mg/600 mg/800 mg; n = 3 per cohort). No DLTs were reported in Parts 1 and 2. In Part 3, 121 pts were treated (97 [80%] male, median age 61 years [range 23–80]); Cohorts A/B/C/D included 33/33/20/35 pts. All-grade adverse events (AEs) and treatment-related AEs (TRAEs) were experienced by 96 (79%) and 47 (39%) pts, respectively. The most commonly reported AEs (all/≥G3) were pyrexia (21%/0%), decreased appetite (17%/2%), anemia (11%/6%), and nausea (9%/0%). 36 (30%) pts reported immune-related AEs, most commonly hypothyroidism, in 7 (6%) pts. Confirmed PR was observed in 6 pts (5%; Cohort A/B, n = 4/2) and 35 (29%) pts had stable disease (Cohort A/B/C/D, n = 9/11/10/5). Conclusions: MTD was not reached for BI 754091 monotherapy or for BI 754091 in combination with BI 754111. The recommended dose for the combination was determined as BI 754091 240 mg plus BI 754111 600 mg q3w. Treatment was well tolerated and consistent with that observed in the global trial. Preliminary anti-tumor activity was seen. Clinical trial information: NCT03433898 .

229 Background: HER2 dual blockade showed the promise in clinical trials in patients (pts) with HER2-positive (HER2-Pos) metastatic colorectal cancer (mCRC). A phase I/II study of a novel anti-HER2 antibody-drug conjugate (HER2-ADC) showed promising activities across different cancer subtypes including HER2-Pos mCRC, and also showed a hint of activity for low-expressing (HER2-L) mCRC, regardless of RAS mutation. However, molecular landscape and prognostic value of HER2-L on mCRC are unclear. Methods: The eligibility included pts with mCRC who had undergone surgical resection of primary tumor. Using the specimen, HER2 expression was evaluated by immunohistochemistry (IHC) and FISH. Definition of HER2 positivity was as follows; HER2-Pos as IHC 3+ or IHC 2+/FISH positive: HER2-L as IHC 2+/FISH negative or IHC 1+: Negative (HER2-Neg) as IHC 0+. NGS tests were also done. Results: Between 2005 and 2015, a total of 370 pts were analyzed; 60% were male, with a median age of 64 y/o. Fifteen pts (4%) with HER2-Pos, 21 (6%) with HER2-L, and 334 (90%) with HER2-Neg were identified. Proportion of left-sided primary tumor was similar among groups ranging from 72% to 78%. No difference was observed in terms of major clinicopathological characteristics. The proportion of co-altered RAS mutations in HER2-L was significantly higher than HER2-Pos ( p = 0.037) and similar to HER2-Neg (27% in HER2-Pos vs. 62% in HER2-L vs. 56% in HER2-Neg). As of median follow-up of 24.8 months, median overall survival (mOS) in HER2-L was significantly better than that in HER2- Pos ( p = 0.029, 18.2 months in HER2-Pos vs. 33.3 in HER2-L vs. 27.9 in HER2-Neg). In 58 pts harboring RAS wild-type who received an anti-EGFR monoclonal antibody therapy, median progression-free survival (mPFS) in HER2-L tended to be better than that in HER2- Pos, with 2.2 months in HER2-Pos, 7.8 in HER2-L, and 5.5 in HER2-Neg ( p = 0.099). Conclusions: Since HER2-L mCRC had the high prevalence of co-altered RAS mutations but showed a better prognosis and might benefit more from an anti-EGFR therapy than HES2-Pos, the HER2-L mCRC seems to have a different biological behavior from HER2-Pos in terms of molecular landscape and prognostic value on mCRC.

e14115 Background: In clinical practice, the shifting use of PD-1 inhibitors and its ligand PD-L1 inhibitors due to ineffectiveness or toxicity is becoming more common and has distinct responses. To validate clinical observation, we examined the anti-cancer effect, tumor microenvironment (TME) modulation and toxicity of dual blockade of PD-1 and PD-L1 in mice. Case Presentation: Three patients with metastatic lung adenocarcinoma received nivolumab (5, 5 and 11 doses); after the initial response and subsequent progression, they were shifted to receive atezolimumab (1, 1 and 4 doses) at intervals of 70, 38 and 43 days, respectively. All 3 patients obtained partial response according to iRECIST. Two of the 3 patients developed pneumonitis at days 3 and 15 after the first dose of atezolimumab and pneumonitis subsided by methylprednisolone injection for 7 and 4 days. Methods: The Balb/c mice bearing lung metastasis of CT26 colon cancer cells were treated. Assessments included optical imaging for tumor burden, multi-parameter flow cytometry for TME, pathology and immuohistochemistry. Results: The pathology of lung showed that all the mice (100%, n = 3 for each group) treated with a combination of anti-PD-1 and anti-PD-L1, either sequential or simultaneous, developed severe clustered inflammatory infiltrates, mucus filling in bronchus and thrombi in small vessels. Among infiltrating leukocytes, combinatorial blockade increased LyC6+ inflammatory monocytes and NKG2D+ T cells and reduced tumor-associated macrophages in lung. Peripheral leukocytes in spleen had no such alteration. In lung metastatic foci, the expression of PD-1 was noted mainly within tumors, and this expression was reduced by combinatorial blockade. PD-L1 expression had no change. For control of lung metastasis, the combinatorial treatments exhibited better control, and anti-PD-L1 followed by anti-PD-1 was the most effective. No significant pneumonitis was noted in single blockade groups. Conclusions: The combination of PD-1 and PD-L1 blockade, either sequential or concurrent, may have better tumor control but cause severe pneumonitis. Dual blockade of PD-1 and PD-L1 should be used with caution.

e12061 Background: Neoadjuvant treatment in HER2 overexpressing early breast cancer (EBC) has increased considerably. The Neosphere study, in which dual blockade of HER2 was combined with docetaxel resulted in favorable pCR rates. The addition of anthracyclines could play an important role in enhancing the effectiveness. The use of NPLD might be valuable in combination with HER2 targeted therapies. Safety and efficacy of NPLD, taxotere and trastuzumab was reported in the ABSCG 32 study. There is only little data about the cardiac safety and efficacy in combination with dual HER2 blockade. We report pCR-rate and cardiac safety of a single arm, retrospective, multicenter analysis of neoadj. treatment for HER2+ EBC. Methods: In this study 98 women with HER2+ EBC were investigated in 4 oncological departments in Austria. All patients were treated with NPLD (50 mg/m²), docetaxel (75 mg/m²) concurrent with trastuzumab and pertuzumab in standard dosage for 6 cycles as neoadjuvant therapy. All patients were free of cardiovascular disease and had a left ventricular ejection fraction (LVEF) of ≥50%. Cardiac function was measured by LVEF. All patients underwent surgery after neoadjuvant chemotherapy. The absence of any residual invasive cancer in the breast and axilla was defined as pathological complete response (pCR). Median follow up was 1.7 years. Results: Median age was 49 years. pCR rate was 73%. In this cohort a negative estrogen-and progesteron receptor was predictive for pCR (p

518Background: In HER2+ EBC pCR rates after neoadjuvant chemo (CT)+/- anti-HER2 therapy differ according to hormone receptor (HR) status. The neoadjuvant ADAPT HER2+/HR- phase II trial aims to iden...

4019 Background: Targeting a single pathway in pancreatic adenocarcinoma (PAC) is unlikely to impact its natural history. EGFR targeting with erlotinib added to gemcitabine (G) marginally improved the outcome of patients with advanced disease. We tested the hypothesis that if the EGFR and IGF-1R pathways are simultaneously blocked then progression free survival (PFS) would be significantly improved by abrogating reciprocal signaling that leads to resistance to either drug. Methods: This was a phase I/randomized phase II (RP2) study testing the anti-IGF-1R monoclonal antibody cixutumumab combined with erlotinib and G in patients with metastatic PAC. The control arm was erlotinib plus G. The primary endpoint of the RP2 portion of the study was PFS. Eligibility included patients with untreated metastatic disease, performance status 0/1, fasting blood glucose less than institutional upper limit of normal, and willingness to provide tissue and blood specimens for correlative studies. Results: In phase I portion (n=10) safety of cixutumumab 6 mg/kg IV/wk, erlotinib 100 mg/day orally and G 1000 mg/m2 IV D 1, 8, and 15 of a 28-day cycle was established. In the RP2 portion (n=124) 114 eligible patients (median age 63) were included. On the cixutumumab arm, 59% of patients were female vs. 40% on control arm. Median PFS and overall survival were 3.7 and 6.7 months, respectively, in both arms of the study. Major grade 3 and 4 toxicities were (cixutumumab/control) elevation of transaminases (12%/6%), fatigue (16%/12%), gastrointestinal (35%/28%), neutropenia (21%/10%), and thrombocytopenia (16%/7%). Grade 3/4 hyperglycemia was seen in 16% of patients on cixutumumab. Grade 3 or 4 kin toxicity was similar in both arms of the study (< 5%). Five treatment-related deaths were reported: 2 cardiac on each arm, 1 pulmonary on cixutumumab. Conclusions: IGF-1R inhibitor cixutumumab did not improve the progression free or overall survival of patients with metastatic PAC treated with erlotinib and G in a molecularly unselected population.

7170 Background: Recent data has shown that the benefit of EGFR TKIs (tyrosine kinase inhibitors) in NSCLC is in patients with tumors that have EGFR mutations and /or gene amplification. Even among these patients, the median survival with EGFR TKIs is only 22 months. Pre-clinical data has shown that dual blockade of EGFR and COX 2 pathways may be beneficial. A recent clinical trial conducted at our center suggested that this combination primarily impacted NSCLC tumors that have the EGFR biomarkers. We therefore hypothesized that the EGFR biomarker status determines the outcome of dual blockade of these pathways in NSCLC. Methods: Three different cell lines with varying biomarker status and sensitivities to EGFR TKIs were used- H3255 (L858R; gene amplified), H1650 (del E746-A750; gene amplified), H1781 (wild type). Cells were treated with erlotinib, EGFR TKI- 10nM-100nM or celecoxib, COX 2 inhibitor- 5 μM and with the combination of two drugs. Cell survival was determined by a standard MTT assay and apoptosis was measured by ELISA method. Western blot analysis was conducted to assess COX 2, EGFR and pAkt levels. Results: Celecoxib by itself had no effects on any of the cell lines. Erlotinib showed a concentration dependent growth inhibition of both H3255 (IC50–41.72nM; surviving fraction at 50nM was 52%) and H1650 (IC50 > 100nM; Surviving fraction at 50nM was 70%) but had no effect on H1781. Celecoxib added to erlotinib significantly enhanced the growth inhibition of H3255 (p = 0.001) and H1650 (p = 0.014) as well as apoptosis (H3255- p = 0.016; H1650- p = 0.011) at all concentrations of erlotinib but had no effect in H1781 cells. In western Blot analysis the combination significantly reduced levels of COX-2, EGFR and pAkt compared to baseline and either agent alone in H3255 cells. Conclusions: The addition of celecoxib to erlotinib has a differential effect in NSCLC cell lines based on their EGFR biomarker status. This beneficial effect of celecoxib addition may be through improved inhibition of each pathway. [Table: see text]