Kim, Kevin

TPS629 Background: The anti–PD-L1 antibody ATEZO prevents PD-L1 from interacting with PD-1 and B7.1, thus reinvigorating antitumor T cell activity. Anti-VEGF BEV can increase dendritic cell maturation, enhance T cell infiltration, and reduce myeloid-derived suppressor cells and regulatory T-cells in tumors. This combination has been FDA approved for first-line treatment of advanced HCC based on the IMbrave150 study. On the other hand, locoregional radiotherapy (e.g., Y90 TARE) enhances the diversity of the intratumoral T cell receptor repertoire. It is the standard of care for pts with intermediate-stage HCC (iHCC). Based on preclinical and clinical data, we hypothesize that the combination of Y90 TARE, BEV, and ATEZO induces synergistic tumor-killing. Methods: This is an open-label, multicenter, randomized phase II study of Y90 TARE and BEV plus ATEZO compared with Y90 TARE alone in pts with unresectable IHCC (NCT04541173). The primary study objective is to assess and compare the progression-free survival (PFS) (per mRECIST 1.1) of pts in each arm. The main secondary objective is to determine the safety and tolerability (CTCAE v5) of TARE combined with ATEZO and BEV in pts with HCC. Exploratory objectives are to assess the role of the immunoscore and PD-L1 expression levels in the prediction of improved clinical outcome in pts receiving Y-90 TARE and BEV plus ATEZO; the composition of tumor-infiltrating immune cell subtypes in predicting response to a chosen therapy; how Y90 therapy affects the proportion of antigen-presenting cells in the tumor; and symptoms experienced by pts receiving TARE and BEV plus ATEZO treatment, using patient-reported outcomes. Eligible pts have either HCC that is not amenable to surgical resection, confirmed by pathology review, or at least BCLC stage B HCC outside of downstaging criteria. Other standard eligibility criteria apply. Pts must have a pretreatment liver biopsy taken and then be randomized 1:1 to TARE (Arm A) or TARE followed by ATEZO and BEV (Arm B). Pts will have TARE mapping during week (wk) 1 and TARE treatment during wk 2. In Arm B, pts will start BEV plus ATEZO 4 wks (±1 wk) after TARE treatment. Pts will have abdominal MRI or CT scans every 12 weeks, CT scans of the chest every 24 wks. Disease progression will be captured by both RECIST 1.1 and mRECIST. We plan to assess the safety of TARE with BEV and ATEZO in the first 10 pts randomized to Arm B for two cycles. If there are no Grade ≥ 3 unexpected toxicities possibly, probably or definitely related to combined TARE plus BEV plus ATEZO, the study will continue to accrue 128 pts in total. Pts will continue study treatment (Arm B) for a total of 24 months from initiation of TARE or until intolerable toxicity or disease progression occur, whichever is earlier. Clinical trial information: NCT04541173 .

TPS4177 Background: The anti–PD-L1 antibody atezolizumab (ATEZO) prevents PD-L1 from interacting with PD-1 and B7.1, thus reinvigorating antitumor T cell activity. Anti-VEGF bevacizumab (BEV) increases dendritic cell maturation, enhances T cell infiltration, and reduces myeloid-derived suppressor cells and regulatory T cells in tumors. ATEZO + BEV is FDA approved for first-line treatment of advanced HCC based on the IMbrave 150 study. Locoregional radiotherapy (e.g., Y90 TARE) enhances the diversity of the intratumoral T cell receptor repertoire and increases tumor antigen release. We hypothesize that the Y90 TARE + BEV + ATEZO combination induces synergistic tumor killing and prolongs progression-free survival in patients (pts) receiving Y90 TARE (HR = 0.6 when compared to Y-90 TARE alone). Methods: Eligible pts have HCC that cannot be surgically resected (confirmed by pathology review), is at least BCLC stage B, and is outside Milan criteria. Other requirements include ECOG PS of 0-1 at screening, measurable disease by RECIST 1.1, no prior systemic therapy, and FLR estimated at ≥ 40% post local therapy. Pts must have a pretreatment liver biopsy taken and then be randomized 1:1 to TARE (Arm A) or TARE + ATEZO + BEV (Arm B). Pts will have TARE mapping followed by TARE treatment. In Arm B, pts will begin TARE treatment followed by BEV + ATEZO (4 wks [± 1 wk] later). Pts will have abdominal MRI or CT scans every 12 weeks and CT scans of the chest every 24 wks. The primary study objective is to assess and compare pts' progression-free survival (per mRECIST 1.1) in each study arm. The main secondary objective is to determine the safety and tolerability (CTCAE v5) of pts in Arm B. Exploratory objectives are to define the use of cellular and circulating biomarkers in the prediction of improved clinical outcomes of pts in Arm B. Symptoms experienced by pts in both arms using patient-reported outcomes will be assessed. Disease progression will be captured by both RECIST 1.1 and mRECIST. We plan to assess the safety of Y90 TARE + BEV + ATEZO in the first 10 pts randomized to Arm B for two cycles, and if there are no grade ≥ 3 unexpected toxicities possibly, probably, or definitely related to combined TARE + BEV + ATEZO, continue to accrue 128 pts in total (current enrollment n- = 5). Pts will continue study treatment (Arm B) for a total of 24 months from initiation of TARE or until intolerable toxicity or disease progression occur, whichever is earlier. Enrollment began in September 2020. Clinical trial information: NCT04541173.

TPS358 Background: The anti–PD-L1 antibody ATEZO prevents PD-L1 from interacting with PD-1 and B7.1, thus reinvigorating antitumor T cell activity. Anti-VEGF BEV can increase dendritic cell maturation, enhance T cell infiltration, and reduce myeloid-derived suppressor cells and regulatory T-cells in tumors. This combination has been FDA approved for first-line treatment of advanced HCC based on the IMbrave 150 study. On the other hand, locoregional radiotherapy (e.g., Y90 TARE) enhances the diversity of the intratumoral T cell receptor repertoire. It is the standard of care for pts with intermediate-stage HCC (iHCC). Based on preclinical and clinical data, we hypothesize that the combination of Y90 TARE, BEV, and ATEZO induces synergistic tumor-killing. Methods: This is an open-label, multicenter, randomized phase II study of Y90 TARE and BEV plus ATEZO compared with Y90 TARE alone in pts with unresectable IHCC. The primary study objective is to assess and compare the progression-free survival (PFS) (per mRECIST 1.1) of pts in each arm. The main secondary objective is to determine the safety and tolerability (CTCAE v5) of TARE combined with ATEZO and BEV in pts with HCC. Exploratory objectives are to assess the role of the immunoscore and PD-L1 expression levels in the prediction of improved clinical outcome in pts receiving Y-90 TARE and BEV plus ATEZO; the composition of tumor-infiltrating immune cell subtypes in predicting response to a chosen therapy; how Y90 therapy affects the proportion of antigen-presenting cells in the tumor; and symptoms experienced by pts receiving TARE and BEV plus ATEZO treatment, using patient-reported outcomes. Eligible pts have either HCC that is not amenable to surgical resection, confirmed by pathology review, or at least BCLC stage B HCC outside of downstaging criteria. Other standard eligibility criteria apply. Pts must have a pretreatment liver biopsy taken and then be randomized 1:1 to TARE (Arm A) or TARE followed by ATEZO and BEV (Arm B). Pts will have TARE mapping during week (wk) 1 and TARE treatment during wk 2. In Arm B, pts will start BEV plus ATEZO 4 wks (±1 wk) after TARE treatment. Pts will have abdominal MRI or CT scans every 12 weeks, CT scans of the chest every 24 wks, and a second tumor biopsy at 4 wks. Disease progression will be captured by both RECIST 1.1 and mRECIST. We plan to assess the safety of TARE with BEV and ATEZO in the first 10 pts randomized to Arm B for two cycles. If there are no grade ≥ 3 unexpected toxicities possibly, probably or definitely related to combined TARE plus BEV plus ATEZO, the study will continue to accrue 128 pts in total. Pts will continue study treatment (Arm B) for a total of 24 months from initiation of TARE or until intolerable toxicity or disease progression occur, whichever is earlier. Enrollment began in September 2020. Clinical trial information: NCT04541173.

9016 Background: The MAP kinase (MAPK) pathway is of critical importance for keratinocyte proliferation and maturation and is essential for epidermal homeostasis. Occurrence of hyperproliferative skin lesions including keratoacanthomas (KA) and cuSCC are considered a class effect of BRAFi [Anforth 2012, Chu 2012, Mattei 2012]. These effects, as well as promotion of pre-existing RAS-driven malignancies, may be caused by paradoxical activation of the MAPK pathway downstream of BRAF in wild-type BRAF cells. As MEK inhibition blocks downstream MAPK signaling, it was hypothesized that addition of a MEKi to a BRAFi would abrogate these effects [Su, 2012]. Methods: This 4-part phase I/II study enrolled 365 BRAFV600E/Kmutated MM pts in Parts B-D. In part C, 162 pts (BRAFi and MEKi treatment-naïve, ≥ 18 yrs; ECOG PS <2; RECIST measurable disease) were randomized to D monotherapy 150mg BID (D mono) vs. the combination of D (150 mg BID) and T (1 mg or 2 mg QD). Primary endpoints included safety and efficacy. Occurrence of cuSCC (including KA) across three arms in Part C and secondary malignancies with D+T across all Parts are provided below. Results: The difference in incidence of cuSCC between D mono and the D+T (150/1) was statistically significant, whereas the difference in incidence between D mono and D+T (150/2) was not. The median time to onset of cuSCC was 30 days in D mono compared to 282 and 152 days with D+T (150/1 and 150/2, respectively). Of 365 pts who received D+T, 2 (<1%) cases of new cancers (colorectal and gliobastoma) and 2 (<1%) cases of new primary malignant melanoma were reported. Conclusions: These data support the experimental hypothesis that the occurrence of cuSCC (including KA) can be substantially reduced and delayed by the addition of a MEKi to BRAFi therapy. Clinical trial information: NCT01072175. [Table: see text]

9005 Background: Dual inhibition of the MAP kinase (MAPK) pathway with dabrafenib (D) and trametinib (T) in combination has demonstrated clinical benefit compared to D alone in a randomized Phase II trial in V600 BRAF-mutant MM pts, thus delaying the development of BRAFi resistance. Little is known about the efficacy of D + T after BRAFi resistance has been acquired. This analysis evaluates the ability of D + T combination to treat acquired resistance compared to the D + T combination as first-line treatment. Methods: These data from a phase I/II study include 1. BRAFi-resistant group: pts who received 150/2 D+T in Part B (n=26) and Part C (n=43) following progression on BRAFi monotherapy (mono); 2. BRAFi-naïve group: pts who received initial 150/2 D+T in Part B (n=24) and Part C (n=54). Results: Baseline characteristics (ECOG PS, M staging, LDH) were similar across all groups.In the Part B BRAFi-resistant group, 93% of pts previously received D or vemurafenib and all pts received D prior to D+T in Part C. In BRAFi-resistant group, prior best response of CR/PR (38%, 56%), SD (35%, 27%), PD (27%, 7%) was observed in Parts B and C respectively. In BRAFi-resistant group, the ORR and PFS with D+T was lower than initial D+T in BRAFi-naive group. Median duration of response (DoR) in BRAFi-resistant group cannot be calculated due to small no. of pts responding. Median DoR for BRAFi-naïve pts was 11.3 mo and 10.5 mo in Parts B and C respectively. In Part C, the 12-mo overall survival rates in BRAFi-naïve (150/2) pts was 79% vs 70% for pts initially on D mono, despite 80% pts crossing over to D+T combination. Conclusions: The clinical activity for 150/2 D+T combination is consistently superior in BRAFi-naive group vs BRAFi-resistant group in both Parts B and C. Dual MAPK blockade can delay clinical resistance to BRAF inhibition. However, once BRAFi resistance has occurred, the combination of BRAFi + MEKi is far less effective. Clinical trial information: NCT01072175. [Table: see text]