Ex vivo drug response profiling for response and outcome prediction in hematologic malignancies: the prospective non-interventional SMARTrial

Ex vivo drug response profiling is a powerful tool to study genotype-drug response associations and is being explored as a tool set for precision medicine in cancer. Here we conducted a prospective non-interventional trial to investigate feasibility of ex vivo drug response profiling for treatment guidance in hematologic malignancies (SMARTrial, NCT03488641 ). The primary endpoint to provide drug response profiling reports within 7 d was met in 91% of all study participants (N = 80). Secondary endpoint analysis revealed that ex vivo resistance to chemotherapeutic drugs predicted chemotherapy treatment failure in vivo. We confirmed the predictive value of ex vivo response to chemotherapy in a validation cohort of 95 individuals with acute myeloid leukemia treated with daunorubicin and cytarabine. Ex vivo drug response profiles improved ELN-22 risk stratification in individuals with adverse risk. We conclude that ex vivo drug response profiling is clinically feasible and has the potential to predict chemotherapy response in individuals with hematologic malignancies beyond clinically established genetic markers

Tumor Evolution through Differentiation in B-Cell Lymphomas

Since the dawn of multicellular life, cells have diversified through the differentiation of functionally distinct cell types. These cell types give rise to different cancer types and subtypes, with cell of origin central to intertumor heterogeneity. For example, B-cell non-Hodgkin lymphomas are tied to distinct stages of B-cell maturation. In contrast, intratumor heterogeneity, intrinsic to cancer evolution and treatment response, is typically considered distinct from cell-type differentiation. In this thesis, I challenged this view by investigating whether cell-type differentiation influences intratumor heterogeneity in B-cell lymphomas. Through joint single-cell transcriptomic and surface epitope profiling of diffuse large B-cell (DLBCL), mantle cell (MCL), follicular (FL), and marginal zone (MZL) lymphomas from 43 patients, alongside 8 reactive lymph nodes, I found that individual tumors were comprised of multiple B-cell maturation states, suggesting ongoing differentiation from the cell of origin. Tumor maturation state composition varied across and within lymphoma entities, blurring entity boundaries. Cell-of-origin classifiers revealed the presence of mixed germinal center (GCB) and activated B-cell (ABC) clinical subtypes within DLBCL and FL tumors. Varying tumor maturation state composition over time indicates tumors evolve through differentiation, maintained by differentially active maturation transcription factors observed between tumor maturation states. Highly multiplexed immunohistochemistry revealed intratumor maturation states occupy distinct spatial niches, differing in immune infiltration while maintaining maturation-associated cellular interactions. Intratumor maturation states were subject to copy number variation and showed varying expression patterns of mutated genes, suggesting that differentiation and genetic variation are interconnected in cancer. My findings put forward a model of tumor evolution in which cancer cells achieve diversification through cell-type differentiation. Mutability of cell types in cancer poses challenges and opportunities for cancer diagnosis, whereby tumors are not tied to their cell of origin, and cancer treatment, which may need to account for diverse and evolving spectra of cancer cell types. These insights open a wealth of future research avenues in clonal evolution, drug resistance, and precision medicine across cancers

Polatuzumab vedotin as a salvage and bridging treatment in relapsed or refractory large B-cell lymphomas

The antibody-drug conjugate polatuzumab vedotin (pola) has recently been approved in combination with bendamustine and rituximab (pola-BR) for patients with refractory or relapsed (r/r) large B-cell lymphoma (LBCL). To investigate the efficacy of pola-BR in a real-world setting, we retrospectively analyzed 105 patients with LBCL who were treated in 26 German centers under the national compassionate use program. Fifty-four patients received pola as a salvage treatment and 51 patients were treated with pola with the intention to bridge to chimeric antigen receptor (CAR) T-cell therapy (n = 41) or allogeneic hematopoietic cell transplantation (n = 10). Notably, patients in the salvage and bridging cohort had received a median of 3 prior treatment lines. In the salvage cohort, the best overall response rate was 48.1%. The 6-month progression-free survival and overall survival (OS) was 27.7% and 49.6%, respectively. In the bridging cohort, 51.2% of patients could be successfully bridged with pola to the intended CAR T-cell therapy. The combination of pola bridging and successful CAR T-cell therapy resulted in a 6-month OS of 77.9% calculated from pola initiation. Pola vedotin-rituximab without a chemotherapy backbone demonstrated encouraging overall response rates up to 40%, highlighting both an appropriate alternative for patients unsuitable for chemotherapy and a new treatment option for bridging before leukapheresis in patients intended for CAR T-cell therapy. Furthermore, 7 of 12 patients with previous failure of CAR T-cell therapy responded to a pola-containing regimen. These findings suggest that pola may serve as effective salvage and bridging treatment of r/r LBCL patients