Miller, Langdon L.

AbstractRichter syndrome (RS) represents the transformation of chronic lymphocytic leukemia (CLL), typically to an aggressive lymphoma. Treatment options for RS are limited and the disease is often fatal. Receptor tyrosine kinase–like orphan receptor 1 (ROR1) is expressed on CLL cells and other cancers but not on healthy adult tissues, making it an attractive, tumor-specific therapeutic target. VLS-101 is being developed as an antibody-drug conjugate (ADC) for therapy of ROR1-expressing (ROR1+) cancers. VLS-101 comprises UC-961 (a humanized immunoglobulin G1 monoclonal antibody that binds an extracellular epitope of human ROR1), a maleimidocaproyl-valine-citrulline-para-aminobenzoate linker, and the antimicrotubule cytotoxin monomethyl auristatin E (MMAE). VLS-101 binding to ROR1 results in rapid cellular internalization and delivery of MMAE to induce tumor cell death. We studied 4 RS patient-derived xenografts (RS-PDXs) with varying levels of ROR1 expression (11%, 32%, 85%, and 99% of cells). VLS-101 showed no efficacy in the lowest-expressing RS-PDX but induced complete remissions in those with higher levels of ROR1 expression. Responses were maintained during the posttherapy period, particularly after higher VLS-101 doses. In systemic ROR1+ RS-PDXs, VLS-101 dramatically decreased tumor burden in all RS-colonized tissues and significantly prolonged survival. Animals showed no adverse effects or weight loss. Our results confirm ROR1 as a target in RS and demonstrate the therapeutic potential of using an ADC directed toward ROR1 for the treatment of hematological cancers. A phase 1 clinical trial of VLS-101 (NCT03833180) is ongoing in patients with RS and other hematological malignancies.

8017 Background: LAM-002 is a selective inhibitor of PIKfyve that disrupts lysosomal homeostasis, inducing cytotoxicity in B-cell lymphoma models as monotherapy or with anti-CD20 or anti-PDL1 antibodies (Gayle et al., Blood 2017;129(13):1768). Methods: In this study, patients received LAM-002 orally 2-3 times per day (BID or TID) in a 3+3 escalation. Additional patients received LAM-002 125 mg BID as monotherapy; with rituximab 375 mg/m2 intravenously (IV) and or subcutaneously weekly (Q1W) x 4 → Q8W x 4; or atezolizumab 1200 mg IV Q3W until disease progression or unacceptable toxicity. Pharmacokinetics (PK) were assessed for 8 hours postdose on Days 1 and 8. Efficacy was evaluated Q6-12W. Results: The study enrolled 62 patients (M:F n = 32/30); median [range] age = 69 [46-89] years; with diagnoses (n) of diffuse large B-cell lymphoma (25), follicular lymphoma (19), marginal zone lymphoma (8), mantle cell lymphoma (5), or chronic lymphocytic leukemia (5) to receive LAM-002 alone (n) at 50 mg BID (3), 100 mg BID (8), 150 mg BID (8), 75 mg TID (4), or 125 mg BID (20); LAM-002/rituximab (12); or LAM-002/atezolizumab (7). During LAM-002 dose-ranging (50 mg BID → 100 mg BID → 150 mg BID → 75 mg TID → 125 mg BID) transient, reversible nausea and/or diarrhea occurred at 150 mg BID and 75 mg TID, resulting in a LAM-002 recommended Phase 2 dosing regimen (RP2DR) of 125 mg BID. Among 39 patients receiving LAM-002, 125 mg BID, alone or in combination for up to 22 cycles (1.9 years), adverse events were typically low-grade. LAM-002 PK showed rapid absorption, dose proportionality, minimal accumulation, and no substantive changes with rituximab or atezolizumab coadministration. In patients with follicular lymphoma and median [range] prior therapies = 3 [1-9] treated with the RP2DR, objective response rates were 2/7 (29%; 1 complete response [CR], 1 partial response [PR]) with LAM-002, 5/8 (63%; 1 CR, 4 PRs) with LAM-002/rituximab, and 2/2 (100%; 2 PRs) with LAM-002/atezolizumab. Conclusions: LAM-002, the first clinical PIKfyve inhibitor, is safe alone or with full-dose anti-CD20 or anti-PD-L1 inhibition. LAM-002 does not cause the myelosuppressive or immune adverse events associated with lenalidomide or PI3K inhibitors. Promising efficacy supports registration-directed Phase 2/3 testing of LAM-002 monotherapy and combination therapy for patients with previously treated follicular lymphoma. Clinical trial information: NCT02594384 .

3583 Background: The novel curaxin CBL0137 intercalates into DNA, interfering with histone/DNA binding. Consequent trapping of histone chaperone FACT leads to MYC, NF-kB, and HSF1 inhibition, p53 activation, and an IFN response. CBL0137 shows broad nonclinical antitumor activity (Gasparian et al. Sci Transl Med. 2011; 3(95):95ra74). Methods: This dose-ranging study assessed the CBL0137 maximum tolerated dose (MTD) and recommended Phase 2 dose (RP2D) and CBL0137 safety, pharmacokinetics (PK), and efficacy in adults with advanced treatment-refractory solid tumors. CBL0137 was administered IV on Days 1, 8, and 15 of repeated 28-day cycles until progressive disease (PD) or unacceptable toxicity. Doses were escalated using a 3+3 design based on Cycle 1 dose-limiting toxicities (DLTs). PK was assessed through 168 hours after Day 1. Efficacy was evaluated every 8 weeks. Results: The study enrolled 83 pts (M/F [n] = 49/34; median [range] age = 64 [33-85] years; ECOG status [n] = 1/2 [32/51]), with cancer types (n) of colorectal (23), prostate (7), glioblastoma (6), liver (6), non-small-cell (5), and others (36) across 17 dose levels from 10 to 700 mg/m2/infusion. Durations of therapy ranged to 24 months. Cycle 1 DLTs (n type) were observed at 240 mg/m2 (1 Gr 3 photosensitivity), 400 mg/m2 (1 Gr 3 anemia), 700 mg/m2 (1 Gr 4 thrombocytopenia, 1 Gr 4 neutropenia/Gr 4 thrombocytopenia), and 650 mg/m2 (1 Gr 3 thrombocytopenia, 1 Gr 4 neutropenia/Gr 3 thrombocytopenia). Nausea and vomiting were successfully prevented with dexamethasone/serotonin antagonists. Photosensitization was effectively managed with sun protection. Peripheral venous thrombosis required central vein infusion in subjects with glioblastoma. PK showed dose-proportional increases in plasma CBL0137 area under the concentration-time curve (AUC), a high mean (range) volume of distribution (Vd) of 1,030 (655-1460) L/m2 consistent with extensive tissue distribution and DNA intercalation, and an average mean (range) half-life (t1/2) of 24.7 (10.3-40.7) hours without dose dependence. The best response was stable disease: 2 pts with liver cancer had tumor control for 9 and 24 months and a maximum tumor regression of 10%; 2 pts with prostate cancer had tumor regressions by 11% and 22%; 1 pt with uterine cancer had a 20% tumor regression. Conclusions: CBL0137 administered IV was generally well tolerated with manageable toxicities The MTD and RP2D were estimated at 540 mg/m2 due to myelosuppressive DLTs. PK were predictable. Preliminary evidence of antitumor activity supports Phase 2 testing. Clinical trial information: NCT01905228 .

ROR1 is a transmembrane receptor with tightly controlled expression during development. It is present on multiple tumor types but not on normal adult tissues. Hematological malignancies are often ROR1-positive, including chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL), and diffuse large B cell lymphoma (DLBCL). Given its unique pattern of expression, ROR1 represents a tumor-specific therapeutic target. The anti-ROR1 antibody, UC-961, is ahumanized IgG1 monoclonal antibody (mAb) that binds with high affinity to a specific extracellular epitope of human ROR1 receptor and can block Wnt5a-induced ROR1 signaling. Nonclinical studies document that UC-961 does not react with normal adult human tissues and selectively binds to tumor cells. Because of the antibody high specificity, rapid internalization, and trafficking to lysosomes, UC-961 appears ideally suited to serve as the targeting moiety for an anti-ROR1 ADC. Accordingly, we have developed VLS-101, a UC-961-linker-monomethyl auristatin E (MMAE) ADC that preserves the high-affinity binding and specificity of UC-961 and allows for ROR1-targeted intracellular release of MMAE. RS is an aggressive lymphoma, typically of DLBCL type, arising as transformation of CLL. Despite, progressive improvements in the therapy of CLL, very few effective treatment options exist for patients with RS. Using our recently established RS patient-derived xenografts (RS-PDXs), we explored the expression and signaling properties of ROR1 in RS and investigated the ex-vivo and in vivo effects of VLS-101. When assessed by flow cytometry (FACS), immunohistochemistry (IHC), and reverse-transcriptase-polymerase chain reaction (RT-PCR), 3 of 4 RS-PDXs showed ROR1 positivity (2 highly positive: 99% and 80% of cells; 1 medium/low positive: 25% of cells by FACS). The extent of ROR1 expression correlated among the 3 assays methods and was consistent with ROR1 expression data reported for non-RS DLBCL samples. When engaged by its ligand Wnt-5a, ROR1 activated downstream targets, Rac1 and RhoA, and induced phosphorylation of the p65 subunit of NF-kB and Jnk in RS cells. When cells purified from RS-PDX tumor masses were exposed to VLS-101 ex-vivo, the drug induced time- and dose-dependent apoptosis, as shown by increases in annexin V/propidium iodide and by Caspase-3 and PARP cleavage. VLS-101 efficacy was then assessed in vivo in both subcutaneous and systemic RS-PDX models. When palpable masses had formed in subcutaneous models, mice were randomly assigned to vehicle or VLS-101, bi-weekly treated for 3 consecutive weeks, and then compared for tumor growth and survival. In the 3 ROR1-expressing RS-PDX models, VLS-101 caused highly significant disease regressions. Complete regressions were observed even in RS-PDXs without universal ROR1 expression, suggesting a MMAE bystander effect. After treatment discontinuation, VLS-101-treated animals showed no tumor regrowth for several months and had significantly extended survival. Data were confirmed in systemic ROR1-expressing RS models in which tumor cells were intravenously injected and allowed to engraft for ~14 days before starting treatment. VLS-101 was administered with the same schedule adopted for the subcutaneous model. VLS-101 eliminated RS cells in bone marrow, peripheral blood, and spleen, increasing survival in VLS-101-treated animals relative to controls (approximately 20-50 days, depending on the RS-PDX model). Of note, no in vivo VLS-101 efficacy was observed in the ROR1-negative RS-PDX, confirming the specificity of VLS-101 targeting. VLS-101 showed no adverse effects on animal well-being or body weight. Collectively, these results indicate that ROR1 is expressed on RS cells where it can transduce pro-survival signals and can be diagnostically evaluated for selective targeting. Nonclinical data document that the MMAE-containing ADC, VLS-101, can cause RS-PDX apoptosis in vitro and can safely and selectively induce complete tumor regressions in in vivo models of RS derived from patient tumors with heavy prior clinical treatment and variable levels of ROR1 expression. Building on these types of results, a Phase 1 clinical trial of VLS-101 (NCT03833180) is ongoing in patients with lymphoid cancers. Disclosures Vaisitti: VelosBio Inc.: Research Funding; Verastem Inc: Research Funding. Jessen:VelosBio Inc.: Employment. Vo:VelosBio Inc: Employment. Ko:VelosBio Inc: Employment. Allan:Sunesis Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics LLC, an AbbVie company: Consultancy; Acerta Pharma: Consultancy; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees; Verastem Oncology, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria; Bayer: Consultancy. Furman:Acerta Pharma: Consultancy; Pharmacyclics: Consultancy; Beigene: Consultancy; AstraZeneca: Consultancy; Genentech: Consultancy; Incyte: Consultancy; Oncotracker: Consultancy; Verastem: Consultancy; Abbvie: Consultancy; Sunesis: Consultancy; TG Therapeutics: Consultancy; Janssen: Consultancy. Miller:VelosBio Inc.: Employment. Lanutti:VelosBio Inc.: Employment. Deaglio:iTeos Therapeutics: Research Funding; Verastem Inc: Research Funding; VelosBio Inc.: Research Funding. OffLabel Disclosure: The drug used in this project is an anti-ROR1-toxin-conjugated antibody

Purpose The traditional end point for assessing efficacy of first-line chemotherapies for advanced cancer is overall survival (OS), but this end point requires prolonged follow-up and is potentially confounded by the effects of second-line therapies. We investigated whether progression-free survival (PFS) could be considered a valid surrogate for OS in advanced colorectal cancer. Patients and Methods Individual patient data were available from 10 historical trials comparing fluouracil (FU) + leucovorin with either FU alone (1,744 patients) or with raltitrexed (1,345 patients) and from three validation trials comparing FU + leucovorin with or without irinotecan or oxaliplatin (1,263 patients). Correlation coefficients were estimated in historical trials between the end points of PFS and OS, and between the treatment effects on these end points. Treatment effects on OS were predicted in validation trials, and compared with the observed effects. Results In historical trials, 1,760 patients (57%) had progressed or died at 6 months, and 1,622 (52%) had died at 12 months. The rank correlation coefficient between PFS and OS was equal to 0.82 (95% CI, 0.82 to 0.83). The correlation coefficient between treatment effects on PFS and on OS ranged from 0.99 (95% CI, 0.94 to 1.04) when all trials were considered to 0.74 (95% CI, 0.44 to 1.04) after exclusion of one highly influential trial. In the validation trials, the observed OS hazard ratios were within the 95% prediction intervals. A hazard ratio of 0.77 or lower in terms of PFS would predict a benefit in terms of OS. Conclusion PFS is an acceptable surrogate for OS in advanced colorectal cancer.

AbstractPurpose: To determine the recommended starting doses and pharmacokinetics of irinotecan in cancer patients with impaired liver function treated on a weekly schedule.Experimental Design: Patients with solid tumors who had impaired liver function were enrolled into four groups based on baseline serum total bilirubin and aspartate aminotransferase (AST)/alanine aminotransferase (ALT): Group 1 (n = 19): total bilirubin 1.5 to 3.0 × institutional upper limit of normal (IULN) and ALT/AST ≤5.0 × IULN; Group 2 (n = 7): total bilirubin 3.1 to 5.0 × IULN and ALT/AST ≤5.0 × IULN; Group 3 (n = 6): total bilirubin ≤1.5 × IULN and ALT/AST 5.1 to 20.0 × IULN; Group 4 (n = 10): total bilirubin 1.5 to 3.0 × IULN and ALT/AST 5.1 to 20.0 × IULN. Irinotecan was given as a 90-minute i.v. infusion weekly for the first 4 weeks in each 6-week cycle at starting doses which escalated from 40 to as much as 75 mg/m2. After the first treatment, doses were adjusted based on individual patient toxicities. Starting doses for patients with hepatic dysfunction were derived from the maximum tolerated doses noted in the four hepatic dysfunction groups.Results: Forty-two patients were treated. Among the most frequent adverse events were neutropenia (41%, grades 3/4), diarrhea (15%, grades 3/4), nausea (10%, grade 3), and vomiting (5%, grades 3/4). Two patients died from drug-induced neutropenic sepsis. Two patients had objective tumor responses (complete response, liver metastases from unknown primary; partial response, colon cancer). Hepatic dysfunction reduced irinotecan clearance while increasing relative exposure to the active metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38). SN-38 exposures in patients receiving doses of 40 to 75 mg/m2 were comparable to exposures in patients with normal liver function treated with a starting dose of 125 mg/m2.Conclusions: Irinotecan starting doses that seem to be safe for hepatically impaired patients treated with the weekly schedule are 60, 50, 60, and 40 mg/m2 for groups 1 to 4, respectively. At these starting doses, exposure to SN-38 and the adverse event profile are similar to that observed in patients with normal liver function and antitumor activity can be observed.