Michael E. Williams

CD24 is highly expressed in aggressive B-cell malignancies and represents a novel immunologic vulnerability to overcome resistance to CD19 chimeric antigen receptor T-cell (CAR-T) therapy. We developed a CD24 × CD3 bispecific antibody (CD24 BsAb) and CXCR3-armed CD24 CAR-T cells, both exhibiting potent antitumor activity in lymphoma and leukemia models. CD24 BsAb and CD24 CAR-T overcome CD19 CAR-T resistance driven by antigen loss and apoptosis defects in vitro and in vivo. Beyond direct cytotoxicity, CD24-targeted T cells reprogram macrophages toward an M1-like phenotype and enhance phagocytic clearance. We further engineered a dual-specific, dual-functional CD19 CAR-T that secretes a CD24 bispecific T-cell engager (CD24 BiTE), enabling simultaneous targeting of CD19 and CD24 to address tumor heterogeneity and achieve superior efficacy. Collectively, our study demonstrates that CD24-directed adoptive T-cell therapies are warranted for B-cell malignancies through robust induction of both innate and adaptive immune responses.

Aggressive B-cell lymphomas, driven by MYC overexpression, exhibit rapid progression, resistance to therapies, and poor survival. While chimeric antigen receptor (CAR)-engineered T cells have demonstrated remarkable clinical efficacy in B-cell lymphomas, nearly half of patients who initially respond to CAR-T therapy eventually develop resistance and disease progression. In this study, we report the presence of residual drug-tolerant persister (DTP) and resistant lymphoma cells remaining within a highly immunogenic tumor microenvironment (TME) induced by the MCL-1 inhibitor (MCL-1i) S63845. MCL-1 inhibition downregulates MYC and activates the STAT1-interferon inflammatory pathway, promoting cytotoxic T-cell infiltration with reduced tumor-associated myeloid cells both in vitro and in vivo. Sublethal dose of the MCL-1i enhances TME immunogenicity and reawakens anti-tumor immune responses in murine models. We show that MCL-1i and CD19-targeted CAR-T cells reciprocally overcome resistance to each single-agent therapy, and combining MCL-1i with CD19 CAR-T cells significantly improves treatment efficacy, resulting in near-complete eradication of MYC-driven lymphoma in vivo. Together, these findings highlight a synergistic, dual-pronged therapeutic strategy targeting both tumor-intrinsic survival pathways and the immunosuppressive TME. This combinatorial one-two-punch approach offers a promising path to eliminate DTP and residual disease, prevent relapse and pave the way for deep clinical remissions in aggressive B-cell lymphomas.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical trial updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported. In 2003, the Eastern Cooperative Oncology Group initiated a randomized phase III clinical trial (E4402) comparing two different rituximab dosing strategies for patients with previously untreated low–tumor burden follicular lymphoma. Rituximab-responsive patients (n = 299) were randomly assigned to either a retreatment rituximab (RR) strategy or a maintenance rituximab (MR) strategy. Each dosing strategy was continued until treatment failure. The primary end point of the study was time to treatment failure (TTF). In the original report, there was no difference in TTF between the two dosing strategies. Here, we report on the long-term outcomes for secondary end points of time to first cytotoxic therapy, duration of response, and overall survival (OS). At 7 years, 83% of MR patients had not required first chemotherapy compared with 63% of RR patients (hazard ratio, 2.37 [95% CI, 1.5 to 3.76]). At 7 years, 71% of MR remained in their first remission compared with 37% of RR patients. Despite the improved first remission length with MR, there was no difference in OS at 10 years (83% v 84%). With mature long-term data, we confirm that prolonged maintenance rituximab does not confer an OS advantage in low–tumor burden follicular lymphoma.

PDF file - 74K, CEP-32496 Supplemental Data.

PDF file - 74K, CEP-32496 Supplemental Data.

Relapsed Mantle cell lymphoma (MCL) is often treated with Bruton's Tyrosine Kinase inhibitors (BTKi); however, post-BTKi relapse can be challenging. Adding venetoclax (VEN) to ibrutinib(IBR) has shown synergy in pre-clinical MCL models. Prior MCL studies of the combination report promising efficacy but have conducted limited dose finding. We sought to identify the optimal dosing combination, based on efficacy and toxicity, utilizing a continual re-assessment method of 6 combinations of IBR (280mg, 420 mg, and 560mg PO daily) and VEN (max dose of 200mg and 400mg PO daily). Eligible participants were not previously exposed to BTKi's and not high risk for Tumor Lysis Syndrome (TLS). VEN, initiated first at 100mg, then at 20mg PO daily after a TLS event, was started prior to adding IBR and ramped-up based on the dose level. Combination treatment continued for six 28 day cycles. 35 participants were enrolled and treated. One TLS event occurred with starting dose of 100mg VEN; no TLS was seen with 20mg. The optimal dosing combination was considered to be VEN 200mg and IBR 420mg with an ORR of 93.8% (95% CI: 73.6-99.7%) and DLT incidence of 6.2% (95% CI: 0.3-26.4%). Overall response for all arms was 82.3% (28/34; 95% CI: 65.5-93.2%) with a CR rate of 42.4% (14/33; 95% CI: 25.5-60.8%). A participant was not allocated to IBR 560mg and VEN 400mg. ORR benefit was not seen with higher dosing combinations and toxicity was higer; a comparison made within the limitations of small cohorts. Resistance was seen in nearly all arms. This trial was registered at www.clinicaltrials.gov #NCT02419560.

The Bcl-2 inhibitor venetoclax has yielded exceptional clinical responses in chronic lymphocytic leukemia (CLL). However, de novo resistance can result in failure to achieve negative minimal residual disease and predicts poor treatment outcomes. Consequently, additional proapoptotic drugs, such as inhibitors of Mcl-1 and Bcl-xL, are in development. By profiling antiapoptotic proteins using flow cytometry, we find that leukemic B cells that recently emigrated from the lymph node (CD69+/CXCR4Low) in vivo are enriched for cell clusters simultaneously overexpressing multiple antiapoptotic proteins (Mcl-1High/Bcl-xLHigh/Bcl-2High) in both treated and treatment-naive CLL patients. These cells exhibited antiapoptotic resistance to multiple BH-domain antagonists, including inhibitors of Bcl-2, Mcl-1, and Bcl-xL, when tested as single agents in a flow cytometry–based functional assay. Antiapoptotic multidrug resistance declines ex vivo, consistent with resistance being generated in vivo by extrinsic microenvironmental interactions. Surviving “persister” cells in patients undergoing venetoclax treatment are enriched for CLL cells displaying the functional and molecular properties of microenvironmentally induced multidrug resistance. Overcoming this resistance required simultaneous inhibition of multiple antiapoptotic proteins, with potential for unwanted toxicities. Using a drug screen performed using patient peripheral blood mononuclear cells cultured in an ex vivo microenvironment model, we identify novel venetoclax drug combinations that induce selective cytotoxicity in multidrug-resistant CLL cells. Thus, we demonstrate that antiapoptotic multidrug-resistant CLL cells exist in patients de novo and show that these cells persist during proapoptotic treatment, such as venetoclax. We validate clinically actionable approaches to selectively deplete this reservoir in patients.

A number of recent therapeutic advances have improved outcomes for mantle cell lymphoma (MCL), both in the front-line and relapsed/refractory settings. With a median age of 65 at diagnosis, many patients are considered ineligible for autologous stem cell transplantation and at risk for increased toxicity from the intensified front-line therapies which are effective in younger patients. In recent years, the field has gained an understanding of the clinical and biologic heterogeneity that in turn may inform front-line therapy and provide options that balance treatment intensity with the special risks faced by older or medically unfit MCL patients. Noting that several key studies are currently underway which could alter this clinical landscape, this review will discuss the current state and evolving standards of care for elderly patients with previously-untreated MCL.

4241 Gemcitabine-based combination regimens have been utilized in the treatment of advanced disease with minimal effect on survival. VEGF and COX-2 overexpression in pancreatic tumor tissue suggest that an anti-angiogenic agent such as thalidomide and a COX-2 inhibitor such as celecoxib may improve response. Addition of celecoxib (C) to thalidomide (T) and gemcitabine (G) was therefore evaluated in a Phase I/II trial. Methods: Twelve patients with unresectable, locally-advanced or metastatic adenocarcinoma of pancreas were enrolled in Phase I/II trial of weekly G(1,000mg/m2) on days 1 and 8 every 21 days. Patients received C 400mg PO BID and T 200mg PO QHS and titrating to 300mg PO QHS if tolerated after one week. C and T were started 2 weeks prior to the first dose of G and continued throughout the treatment. To assess possible response from C and T alone, tumor markers CEA and CA19–9 were followed prior to initiation of G and throughout the course of therapy. Patients were followed closely for major toxicities including neutropenia, renal failure, gastrointestinal hemorrhage, thrombotic events, thrombocytopenia, peripheral neuropathy, somnolence, and rash. Therapy was held or discontinued if significant toxicities developed or if disease had progressed upon clinical or radiographic evaluation. Results: Twelve patients were enrolled. Mean age was 57 years (range 45 to 72) with ECOG status 0,1, or 2 at initiation. Mean number of cycles received was 2.3. Five patients were noted to have a partial biochemical response to C and T alone as evidenced by a decrease in CA19–9 levels. No radiographic responses were noted, although several patients had improvement in metastatic disease or stable disease. Mean survival of patients from time of diagnosis was 10 months. Toxicities included 3 patients with a skin rash and 1 patient with pulmonary embolism. Conclusions: The partial biochemical CA19–9 response of advanced pancreatic cancer to oral C and T alone or in combination with G in a significant fraction of patients suggests anti-tumor activity. Measureable radiographic responses from the combination of G, C and T appear to be no better than single agent G, but the regimen was well tolerated.