Chadburn, Amy

Abstract Castleman disease (CD) describes a group of rare lymphoproliferative disorders that exhibit a wide range of symptomatology and degree of lymphadenopathy, particularly across the 2 forms of CD with unknown etiology, unicentric CD (UCD), and human herpesvirus-8–negative/idiopathic multicentric CD (iMCD). Whereas UCD cases typically present with localized lymphadenopathy and mild symptoms, iMCD involves multicentric lymphadenopathy and cytokine storm–driven symptoms with 3 recognized clinical phenotypes. Increasingly, there are anecdotal reports of cases that do not fit into this framework, but these cases have not been systematically described. Herein, we use the ACCELERATE natural history registry to characterize the spectrum of CD based on disease features, symptomatology, and severity. Our results characterize a cohort of 179 CD cases, which were reviewed and confirmed by an expert panel of clinicians and hematopathologists. We show that patients with CD present on a continuous spectrum of clinical phenotypes, and we describe oligocentric CD (OligoCD), an intermediate phenotype that does not fit the criteria for UCD or iMCD. These cases tend to have “oligocentric” lymphadenopathy (median [interquartile range] regions of lymphadenopathy, 3.0 [2.0-4.0]) in a regional pattern and exhibit a mild clinical phenotype that is more similar to UCD than iMCD. We also show that patients with OligoCD are inconsistently categorized as UCD vs iMCD, highlighting the need for this characterization. Future data collected through ACCELERATE may further elucidate the natural history and risk profile of these patients.

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.

Abstract Castleman disease (CD) includes a group of rare and heterogeneous disorders with characteristic lymph node histopathological abnormalities. CD can occur in a single lymph node station, which is referred to as unicentric CD (UCD). CD can also involve multicentric lymphadenopathy and inflammatory symptoms (multicentric CD [MCD]). MCD includes human herpesvirus-8 (HHV-8)–associated MCD, POEMS-associated MCD, and HHV-8−/idiopathic MCD (iMCD). The first-ever diagnostic and treatment guidelines were recently developed for iMCD by an international expert consortium convened by the Castleman Disease Collaborative Network (CDCN). The focus of this report is to establish similar guidelines for the management of UCD. To this purpose, an international working group of 42 experts from 10 countries was convened to establish consensus recommendations based on review of treatment in published cases of UCD, the CDCN ACCELERATE registry, and expert opinion. Complete surgical resection is often curative and is therefore the preferred first-line therapy, if possible. The management of unresectable UCD is more challenging. Existing evidence supports that asymptomatic unresectable UCD may be observed. The anti–interleukin-6 monoclonal antibody siltuximab should be considered for unresectable UCD patients with an inflammatory syndrome. Unresectable UCD that is symptomatic as a result of compression of vital neighboring structures may be rendered amenable to resection by medical therapy (eg, rituximab, steroids), radiotherapy, or embolization. Further research is needed in UCD patients with persisting constitutional symptoms despite complete excision and normal laboratory markers. We hope that these guidelines will improve outcomes in UCD and help treating physicians decide the best therapeutic approach for their patients.

Follicular lymphoma (FL) is an indolent B-cell neoplasm of germinal center origin. Standard treatment regimens consist of anti-CD20 therapy with or without chemotherapy. While high response rates to initial therapy are common, patients ultimately relapse or have progressive disease. Clinical risk factors such as the Follicular Lymphoma International Prognostic Index (FLIPI) have been identified, but there is a need for prognostic and predictive biomarkers. We studied markers of lymphoma cells and tumor microenvironment by immunohistochemistry in tissue samples from patients enrolled in 1 of 4 phase 2 trials of anti–CD20-based biological therapy for previously untreated grades 1 to 2 or 3A FL. Results were correlated with progression-free survival (PFS) and PFS status at 24 months. The 4 trials included 238 patients (51.1% male, median age: 55 y) with stage III, IV, or bulky stage II disease. By FLIPI, 24.6% had low-risk, 56.8% had intermediate-risk, and 18.6% had high-risk disease. The outcome differed significantly for patients treated with lenalidomide and rituximab (CALGB 50803) compared with the other 3 trials (median: PFS not reached vs. 3.0 y, hazard ratio=3.47, 95% confidence interval: 2.11-5.72); therefore, data were stratified by clinical trial (CALGB 50803 vs. all others) and adjusted for FLIPI risk group. Among 154 patients with available tissue, interfollicular BCL6 positivity, interfollicular CD10 positivity, and elevated Ki67 proliferation index ≥30% within neoplastic follicles were each associated with inferior PFS and a high risk of the early event by PFS status at 24 months. We identify promising biomarkers for FL risk stratification that warrant further validation in phase 3 trials.

AbstractIdiopathic multicentric Castleman disease (iMCD) is a rare immunologic disorder characterized by systemic inflammation, multicentric lymphadenopathy, and organ dysfunction. Enlarged lymph nodes demonstrate a spectrum of characteristic but variable histopathologic features historically categorized into hyaline vascular (HV) (or hypervascular [HyperV] more recently), plasmacytic, or “mixed.” Though the etiology is unknown, a pro‐inflammatory cytokine storm, often involving interleukin‐6 (IL‐6), contributes to pathogenesis. Anti‐IL‐6 therapy with siltuximab is the only FDA‐ or EMA‐approved treatment based on efficacy and safety in multiple studies. Importantly, no patients considered to have HV histopathology achieved the primary endpoint in the Phase II study. NCCN currently recommends siltuximab first‐line for iMCD, except for patients considered to have HV histopathology. We investigated whether histopathologic subtype should guide siltuximab treatment decisions. Secondary analyses of clinical trial and real‐world data revealed similar clinical benefit across histopathologic subtypes. Notably, only 18 of 79 patients in the Phase II study were consistently classified into histopathologic subtype by three independent review panels, demonstrating limited reliability to guide treatment decisions. Real‐world data further demonstrate siltuximab's effectiveness in patients considered to have HV (or HyperV). Though histopathology is a critical component for diagnosis, there is insufficient evidence to guide treatment based solely on lymph node histopathologic subtype.

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 Alliance/CALGB 50303 (NCT00118209), an intergroup, phase III study, compared dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab (DA-EPOCH-R) with standard rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) as frontline therapy for diffuse large B-cell lymphoma. PATIENTS AND METHODS Patients received six cycles of DA-EPOCH-R or R-CHOP. The primary objective was progression-free survival (PFS); secondary clinical objectives included response rate, overall survival (OS), and safety. RESULTS Between 2005 and 2013, 524 patients were registered; 491 eligible patients were included in the final analysis. Most patients (74%) had stage III or IV disease; International Prognostic Index (IPI) risk groups included 26% IPI 0 to 1, 37% IPI 2, 25% IPI 3, and 12% IPI 4 to 5. At a median follow-up of 5 years, PFS was not statistically different between the arms (hazard ratio, 0.93; 95% CI, 0.68 to 1.27; P = .65), with a 2-year PFS rate of 78.9% (95% CI, 73.8% to 84.2%) for DA-EPOCH-R and 75.5% (95% CI, 70.2% to 81.1%) for R-CHOP. OS was not different (hazard ratio, 1.09; 95% CI, 0.75 to 1.59; P = .64), with a 2-year OS rate of 86.5% (95% CI, 82.3% to 91%) for DA-EPOCH-R and 85.7% (95% CI, 81.4% to 90.2%) for R-CHOP. Grade 3 and 4 adverse events were more common ( P < .001) in the DA-EPOCH-R arm than the R-CHOP arm, including infection (16.9% v 10.7%, respectively), febrile neutropenia (35.0% v 17.7%, respectively), mucositis (8.4% v 2.1%, respectively), and neuropathy (18.6% v 3.3%, respectively). Five treatment-related deaths (2.1%) occurred in each arm. CONCLUSION In the 50303 study population, the more intensive, infusional DA-EPOCH-R was more toxic and did not improve PFS or OS compared with R-CHOP. The more favorable results with R-CHOP compared with historical controls suggest a potential patient selection bias and may preclude generalizability of results to specific risk subgroups.

Abstract Castleman disease (CD) describes a group of heterogeneous hematologic disorders with characteristic histopathological features. CD can present with unicentric or multicentric (MCD) regions of lymph node enlargement. Some cases of MCD are caused by human herpesvirus-8 (HHV-8), whereas others are HHV-8–negative/idiopathic (iMCD). Treatment of iMCD is challenging, and outcomes can be poor because no uniform treatment guidelines exist, few systematic studies have been conducted, and no agreed upon response criteria have been described. The purpose of this paper is to establish consensus, evidence-based treatment guidelines based on the severity of iMCD to improve outcomes. An international Working Group of 42 experts from 10 countries was convened by the Castleman Disease Collaborative Network to establish consensus guidelines for the management of iMCD based on published literature, review of treatment effectiveness for 344 cases, and expert opinion. The anti–interleukin-6 monoclonal antibody siltuximab (or tocilizumab, if siltuximab is not available) with or without corticosteroids is the preferred first-line therapy for iMCD. In the most severe cases, adjuvant combination chemotherapy is recommended. Additional agents are recommended, tailored by disease severity, as second- and third-line therapies for treatment failures. Response criteria were formulated to facilitate the evaluation of treatment failure or success. These guidelines should help treating physicians to stratify patients based on disease severity in order to select the best available therapeutic option. An international registry for patients with CD (ACCELERATE, #NCT02817997) was established in October 2016 to collect patient outcomes to increase the evidence base for selection of therapies in the future.

Abstract Richter syndrome represents the evolution of chronic lymphocytic leukemia into an aggressive tumor, most commonly diffuse large B-cell lymphoma. The lack of in vitro and in vivo models has severely hampered drug testing in a disease that is poorly responsive to common chemoimmunotherapeutic combinations as well as to novel kinase inhibitors. Here we report for the first time the establishment and genomic characterization of two patient-derived tumor xenograft (PDX) models of Richter syndrome, RS9737 and RS1316. Richter syndrome xenografts were genetically, morphologically, and phenotypically stable and similar to the corresponding primary tumor. RS9737 was characterized by biallelic inactivation of CDKN2A and TP53, monoallelic deletion of 11q23 (ATM), and mutations of BTK, KRAS, EGR2, and NOTCH1. RS1316 carried trisomy 12 and showed mutations in BTK, KRAS, MED12, and NOTCH2. RNA sequencing confirmed that in both cases &gt;80% of the transcriptome was shared between primary tumor and PDX. In line with the mutational profile, pathway analyses revealed overactivation of the B-cell receptor, NFκB, and NOTCH pathways in both tumors, potentially providing novel tumor targets. In conclusion, these two novel models of Richter syndrome represent useful tools to study biology and response to therapies of this highly aggressive and still incurable tumor. Significance: Two patient-derived xenograft models of Richter syndrome represent the first ex vivo model to study biology of the disease and to test novel therapeutic strategies. Cancer Res; 78(13); 3413–20. ©2018 AACR.

Key Points An international panel established the first ever diagnostic criteria for iMCD based on review of 244 clinical cases and 88 tissue samples. The criteria require multicentric lymphadenopathy with defined histopathology, ≥2 clinical/laboratory changes, and exclusion of iMCD mimics.