Ovarian cancer and malignant mesothelioma frequently express both mesothelin and CA125 (also known as MUC16) at high levels on the cell surface. The interaction between mesothelin and CA125 may facilitate the implantation and peritoneal spread of tumors by cell adhesion, whereas the detailed nature of this interaction is still unknown. Here, we used truncated mutagenesis and alanine replacement techniques to identify a binding site on mesothelin for CA125. We examined the molecular interaction by Western blot overlay assays and further quantitatively analyzed by enzyme-linked immunosorbent assay. We also evaluated the binding on cancer cells by flow cytometry. We identified the region (296 -359) consisting of 64 amino acids at the N-terminal of cell surface mesothelin as the minimum fragment for complete binding activity to CA125. We found that substitution of tyrosine 318 with an alanine abolished CA125 binding. Replacement of tryptophan 321 and glutamic acid 324 with alanine could partially decrease binding to CA125, whereas mutation of histidine 354 had no effect. These results indicate that a conformation-sensitive structure of the region (296 -359) is required and sufficient for the binding of mesothelin to CA125. In addition, we have shown that a single chain monoclonal antibody (SS1) recognizes this CA125-binding domain and blocks the mesothelin-CA125 interaction on cancer cells. The identified CA125-binding domain significantly inhibits cancer cell adhesion and merits evaluation as a new therapeutic agent for preventing or treating peritoneal malignant tumors.

Summary Background Current treatment options for patients with relapsed or refractory (RR) lymphoma and multiple myeloma (MM) are limited, highlighting the unmet need for effective therapies in these disease settings. CUDC-907 is an oral, first-in-class, small molecule that is designed to inhibit both histone deacetylase (HDAC) and phosphoinositide 3-kinase (PI3K) enzymes, which are members of common oncogenic pathways in hematologic malignancies. This study examines CUDC-907 monotherapy in patients with RR lymphoma and MM. Methods This open-label, non-randomized, first-in-man, phase 1 multi-center trial enrolled adult patients with lymphoma or MM who were refractory to or relapsed after ≥2 prior regimens. CUDC-907 was orally administered in a standard 3+3 dose escalation design using three different dosing schedules which enrolled sequentially as follows: once daily (QD), then intermittent twice (BIW) or thrice weekly (TIW) that enrolled simultaneously, and finally five days on/two days off (5/2) in 21-day cycles. Dosing started at 30 mg for QD and 60 mg for other schedules, escalating in 30 mg increments. Patients continued to receive CUDC-907 until disease progression or other treatment discontinuation criteria were met. The primary objective was to determine the maximum-tolerated dose and recommended phase 2 dose (RP2D); secondary objectives were to assess the safety and tolerability, and preliminary anti-cancer activity. Results from the completed dose escalation phase are presented. Safety analyses were conducted in all patients who received at least one dose of study medication; efficacy analyses were conducted in all patients who received at least one dose of study drug and underwent at least one post-baseline response assessment. This ongoing trial is registered at ClinicalTrials.gov, number NCT01742988. Findings Forty-four heavily pretreated patients received CUDC-907 up to a maximum of 60 mg for the QD and 5/2 schedules, and 150 mg for the intermittent schedules in the dose escalation phase. The most common Grade ≥3 adverse events were thrombocytopenia (n=9, 20%), neutropenia (n=3, 7%), and hyperglycemia (n=3, 7%). Dose limiting toxicities (DLTs) were diarrhea and hyperglycemia; no DLTs were observed on the 5/2 schedule. Eleven of 44 patients reported serious AEs, 3 of which were considered treatment-related: epistaxis and the DLTs of diarrhea and hyperglycemia. AEs led to dose reductions in 6 patients and treatment discontinuation in 7 patients. Thirty-seven patients were evaluable for response. Five out of 9 patients with diffuse large B-cell lymphoma (DLBCL) achieved objective responses (2 complete responses [CR], 3 partial responses [PR]). Three of these objective responses (1 CR, 2PR) occurred in patients with transformed follicular (t-FL) DLBCL. Stable disease (SD) has been observed in 21 (57%) of 37 response-evaluable patients including DLBCL, Hodgkin lymphoma (HL), and MM. On the basis of the response and tolerability profile, the RP2D of CUDC-907 was determined to be 60 mg on the 5/2 sch...

Bruton tyrosine kinase inhibitors (BTKi) and venetoclax are currently used to treat newly diagnosed and relapsed/refractory chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). However, most patients eventually develop resistance to these therapies, underscoring the need for effective new therapies. We report results of the phase 1 dose-escalation portion of the multicenter, open-label, phase 1/2 TRANSCEND CLL 004 (NCT03331198) study of lisocabtagene maraleucel (liso-cel), an autologous CD19-directed chimeric antigen receptor (CAR) T-cell therapy, in patients with relapsed/refractory CLL/SLL. Patients with standard- or high-risk features treated with ≥3 or ≥2 prior therapies, respectively, including a BTKi, received liso-cel at 1 of 2 dose levels (50×106 or 100×106 CAR+ T cells). Primary objectives included safety and determining recommended dose; antitumor activity by 2018 International Workshop on CLL guidelines was exploratory. Minimal residual disease (MRD) was assessed in blood and marrow. Twenty-three of 25 enrolled patients received liso-cel and were evaluable for safety. Patients had a median of 4 (range, 2‒11) prior therapies (100% had ibrutinib; 65% had venetoclax) and 83% had high-risk features including mutated TP53 and del(17p). Seventy-four percent of patients had cytokine release syndrome (9% grade 3) and 39% had neurological events (22% grade 3/4). Of 22 efficacy-evaluable patients, 82% and 45% achieved overall and complete responses, respectively. Of 20 MRD-evaluable patients, 75% and 65% achieved undetectable MRD in blood and marrow, respectively. Safety and efficacy were similar between dose levels. The phase 2 portion of the study is ongoing at 100×106 CAR+ T cells.

Background: In CLL/SLL, ibrutinib treatment before leukapheresis improved in vivo and ex vivo expansion of the CD19-directed chimeric antigen receptor (CAR) T cell therapy tisagenlecleucel, and concurrent ibrutinib therapy improved engraftment and therapeutic efficacy of anti-CD19 CAR T cells in human xenograft mouse models (Fraietta et al. Blood. 2016;127:1117-27). Recent studies in patients with R/R CLL suggest that CD19-directed CAR T cell therapy combined with ibrutinib improves response rates with CTL119 and JCAR014 (Gill et al. Blood. 2018;132:298; Gauthier et al. Blood. 2020;135:1650-60). Liso-cel is an investigational, CD19-directed, defined composition, 4-1BB CAR T cell product administered at equal doses of CD8+ and CD4+ CAR+ T cells. We report initial safety and preliminary efficacy from the phase 1 liso-cel and ibrutinib combination cohort of the ongoing phase 1/2 TRANSCEND CLL 004 study (NCT03331198) in patients with R/R CLL/SLL. Methods: Eligible patients with CLL/SLL met ≥1 of the following: 1) received ibrutinib and progressed at time of study enrollment; 2) had high-risk features and received ibrutinib for ≥6 months (mo) with less than a complete response (CR); 3) had a Bruton tyrosine kinase (BTK) or PLCγ2 gene mutation, with or without progression on ibrutinib; 4) had received prior ibrutinib with no contraindication to reinitiating ibrutinib. Baseline disease assessments included bone marrow (BM) biopsy, complete blood count, lymphocyte enumeration, and CT scan. At enrollment, patients started or continued ibrutinib. Patients continued ibrutinib through leukapheresis and for ≥90 days after liso-cel infusion. Patients received liso-cel infusion at 50 × 106 (dose level [DL]1) or 100 × 106 (DL2) CAR+ T cells after 3 days of lymphodepletion with fludarabine/cyclophosphamide. Primary endpoints were safety and to determine the recommended dose (RD) of liso-cel in combination with ibrutinib for R/R CLL/SLL; overall response (OR) rate (CR + CR with incomplete blood count recovery [CRi] + partial response) and pharmacokinetics (PK) were exploratory endpoints. The RD was selected based on the modified toxicity probability interval algorithm. Results: At data cutoff, 19 patients received liso-cel (DL1, n=4; DL2, n=15) with ibrutinib. Median age was 60 (range, 50‒77) years, and 18 patients (95%) had high-risk cytogenetics (del[17p], n=8; TP53 mutation, n=6; unmutated IGHV, n=16). Patients had a median of 4 (range, 2‒11) prior therapies. All patients were R/R to prior ibrutinib; 14 patients (74%) had BTK inhibitor as last prior therapy and 10 (53%) had prior venetoclax. No dose-limiting toxicities were observed at either DL. The most common grade ≥3 treatment-emergent adverse events (TEAEs) were neutropenia/neutrophil count decrease (n=17; 89%), anemia (n=9; 47%), and febrile neutropenia (n=5; 26%; Table). Six patients had infections at DL2: grade 3 and grade 2 lung infection (n=1 each) and grade 2 coccidioidomycosis, scabies, skin, and gum infections (n=1 each). Ibrutinib-related AEs included diarrhea (n=7), hypertension (n=4), atrial fibrillation (n=1), and rash (n=1). No grade 5 TEAEs occurred. Fourteen patients (74%) had cytokine release syndrome (CRS; 1 grade 3) and 6 (32%) had neurological events (NEs; 3 grade ≥3). Seven patients (37%) required tocilizumab and/or corticosteroids to manage CRS and/or NEs. Preliminary PK data showed a median time to peak liso-cel expansion of 11 days across DLs (DL1, 12 days; DL2, 11 days). Of 19 patients with ≥1-mo follow-up, 18 (95%) had an OR (DL2, 100%; DL1, 75%) and 9 (47%) had a CR/CRi. One patient (5%) had stable disease. All ORs were achieved by Day 30 postinfusion, and 15 (83%) of 18 patients maintained their response at 3-mo follow-up. Of 19 patients evaluable for minimal residual disease (MRD), 17 (89%) achieved undetectable MRD in blood via flow cytometry and 15 (79%) in BM by next-generation sequencing (both sensitivity of ≤10-4). Conclusions: Preliminary data show that liso-cel in combination with ibrutinib is associated with manageable safety, including a low incidence of grade 3 CRS and grade ≥3 NEs, and promising efficacy in heavily pretreated patients with R/R CLL/SLL. No clear difference in safety was observed across DLs, and DL2 was selected as the RD for liso-cel in combination with ibrutinib in patients with R/R CLL/SLL. Updated results from the full combination cohort and additional PK/pharmacodynamic data will be reported. Table Disclosures Dorritie: Juno Therapeutics: Research Funding; Kite-Gilead: Research Funding. Munoz:Portola: Research Funding; Incyte: Research Funding; Acrotech/Aurobindo: Speakers Bureau; Alexion: Consultancy; Seattle Genetics: Consultancy, Honoraria, Research Funding, Speakers Bureau; Fosunkite: Consultancy; Pharmacyclics: Consultancy, Research Funding, Speakers Bureau; Innovent: Consultancy; Genentech/Roche: Research Funding, Speakers Bureau; Pfizer: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding, Speakers Bureau; Juno/Celgene/BMS: Consultancy, Research Funding, Speakers Bureau; Janssen: Consultancy, Research Funding, Speakers Bureau; Bayer: Consultancy, Research Funding, Speakers Bureau; Beigene: Consultancy, Speakers Bureau; Millenium: Research Funding; Verastem: Speakers Bureau; Merck: Research Funding; AbbVie: Consultancy, Speakers Bureau; AstraZeneca: Speakers Bureau; Kyowa: Consultancy, Honoraria, Speakers Bureau. Stephens:Innate: Consultancy; Verastem: Research Funding; Beigene: Consultancy; Karyopharm: Consultancy, Research Funding; Acerta: Research Funding; Gilead: Research Funding; Juno: Research Funding; MingSight: Research Funding; Arqule: Research Funding; Janssen: Consultancy; Pharmacyclics: Consultancy. Gillenwater:Juno Therapeutics, a Bristol-Myers Squibb Company: Current Employment; Bristol-Myers Squibb: Current equity holder in publicly-traded company. Gong:Juno Therapeutics, a Bristol-Myers Squibb Company: Current Employment; Bristol-Myers Squibb: Current equity holder in publicly-traded company. Yang:Juno Therapeutics, a Bristol-Myers Squibb Company: Current Employment; Bristol-Myers Squibb: Current equity holder in publicly-traded company. Ogasawara:Bristol-Myers Squibb: Current Employment; Bristol-Myers Squibb: Current equity holder in publicly-traded company. Thorpe:Bristol-Myers Squibb: Current equity holder in publicly-traded company; Juno Therapeutics, a Bristol-Myers Squibb Company: Current Employment. Siddiqi:Astrazenca: Membership on an entity's Board of Directors or advisory committees; PCYC: Membership on an entity's Board of Directors or advisory committees; Juno: Membership on an entity's Board of Directors or advisory committees; Kite: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; BeiGene: Other: DMC member; Juno Therapeutics, Pharmacyclics LLC, an AbbVie Company, AstraZeneca, Celgene, Kite Pharma, and BeiGene: Consultancy; Pharmacyclics LLC, an AbbVie Company, Juno Therapeutics, KITE Pharma, AstraZeneca, TG Therapeutics, Celgene, Oncternal, and BeiGene: Research Funding; Pharmacyclics LLC, an AbbVie Company, Seattle Genetics, Janssen, and AstraZeneca: Speakers Bureau; AstraZeneca: Other: Travel/accommodations/expenses.