Andreas Schröeder

BACKGROUND: The integrity of RNA molecules is of paramount importance for experiments that try to reflect the snapshot of gene expression at the moment of RNA extraction. Until recently, there has been no reliable standard for estimating the integrity of RNA samples and the ratio of 28S:18S ribosomal RNA, the common measure for this purpose, has been shown to be inconsistent. The advent of microcapillary electrophoretic RNA separation provides the basis for an automated high-throughput approach, in order to estimate the integrity of RNA samples in an unambiguous way. METHODS: A method is introduced that automatically selects features from signal measurements and constructs regression models based on a Bayesian learning technique. Feature spaces of different dimensionality are compared in the Bayesian framework, which allows selecting a final feature combination corresponding to models with high posterior probability. RESULTS: This approach is applied to a large collection of electrophoretic RNA measurements recorded with an Agilent 2100 bioanalyzer to extract an algorithm that describes RNA integrity. The resulting algorithm is a user-independent, automated and reliable procedure for standardization of RNA quality control that allows the calculation of an RNA integrity number (RIN). CONCLUSION: Our results show the importance of taking characteristics of several regions of the recorded electropherogram into account in order to get a robust and reliable prediction of RNA integrity, especially if compared to traditional methods.

18 Background: Magrolimab (M, Hu5F9-G4) is an antibody targeting CD47, a “don’t eat me” signal for macrophages that enhances ovarian cancer cell phagocytosis in preclinical models in combination with the PD-L1 inhibitor avelumab. CD47 blockade can also enhance cross-priming of T cells. Methods: In Part 1 (P1) M+A doses were escalated in ST patients (pts) while Part 2 (P2) enrolled platinum-resistant or refractory OC pts. All received a 1 mg/kg Day 1 priming dose of M to mitigate on-target anemia due to macrophage-mediated extravascular hemolysis followed by 30 or 45 mg/kg maintenance doses in P1 or 45 mg/kg in P2, in combination with 800 mg of A Q2 wks. Results: In the 34 total pts (13 in P1 and 21 in P2), median age was 66 years (range 47-88), and median # of prior therapies was 5 (range 1-10). In P1, no dose limiting toxicities occurred. In P1+P2, no Grade (G) 4 or 5 treatment-related adverse events (TRAEs) occurred. TRAEs of any G in > 20% pts included headache 62%, fatigue 47%, infusion related reaction 44%, pyrexia 38%, chills 35%, nausea 35%, anemia 24%, and vomiting 21%. In P1, a patient (pt) with metastatic papillary adenocarcinoma of the finger on 45 mg/kg of M had a confirmed partial response (PR) lasting for 4 months before progressing. In P2, 1 pt had an unconfirmed PR but progressed per RECIST v1.1 on the next scan achieving a best response of stable disease (SD). In the 18 OC P1+P2 pts with at least one response evaluation, 56% had SD and 44% had progression. Analysis of tumor biopsies for immune cells infiltration and CD47, PD-L1, and other marker expression is ongoing. In the 13 OC tumors analyzed to date, only 2 were PD-L1 positive. One PD-L1+ tumor had PD-L1 expression only on infiltrating immune cells. The other PD-L1+ had tumor cell expression and was the only OC pt with tumor shrinkage. This supports the potential importance of PD-L1 expression for this combination. Pharmacokinetic profiles will be presented. Conclusions: M+A is a novel, well-tolerated combination treatment regimen with 1 observed PR in a ST pt and a 56% SD rate in OC pts. Tumor shrinkage was noted in the only OC pt with tumor cell expression of PD-L1 which warrants further evaluation in PD-L1+ OC pts. Clinical trial information: NCT03558139.

A recessive mutation named Justy was found that abolishes B lymphopoiesis but does not impair other major aspects of hematopoiesis. Transplantation experiments showed that homozygosity for Justy prevented hematopoietic progenitors from generating B cells but did not affect the ability of bone marrow stroma to support B lymphopoiesis. In bone marrow from mutant mice, common lymphoid progenitors and pre-pro-B cells appeared normal, but cells at subsequent stages of B lymphopoiesis were dramatically reduced in number. Under culture conditions that promoted B lymphopoiesis, mutant pre-pro-B cells remained alive and began expressing the B cell marker CD19 but failed to proliferate. In contrast, these cells were able to generate myeloid or T/NK precursors. Genetic and molecular analysis demonstrated that Justy is a point mutation within the Gon4-like (Gon4l) gene, which encodes a protein with homology to transcriptional regulators. This mutation was found to disrupt Gon4l pre-mRNA splicing and dramatically reduce expression of wild-type Gon4l RNA and protein. Consistent with a role for Gon4l in transcriptional regulation, the levels of RNA encoding C/EBPalpha and PU.1 were abnormally high in mutant B cell progenitors. Our findings indicate that the Gon4l protein is required for B lymphopoiesis and may function to regulate gene expression during this process.

BACKGROUND: In preclinical studies, combining M9241 (a novel immunocytokine containing interleukin (IL)-12 heterodimers) with avelumab (anti-programmed death ligand 1 antibody) resulted in additive or synergistic antitumor effects. We report dose-escalation and dose-expansion results from the phase Ib JAVELIN IL-12 trial investigating M9241 plus avelumab. METHODS: In the dose-escalation part of JAVELIN IL-12 (NCT02994953), eligible patients had locally advanced or metastatic solid tumors; in the dose-expansion part, eligible patients had locally advanced or metastatic urothelial carcinoma (UC) that had progressed with first-line therapy. Patients received M9241 at 4, 8, 12, or 16.8 µg/kg every 4 weeks (Q4W) plus avelumab 10 mg/kg every 2 weeks (Q2W, dose levels (DLs) 1-4) or M9241 16.8 µg/kg Q4W plus avelumab 800 mg once a week for 12 weeks followed by Q2W (DL5/dose expansion). Primary endpoints for the dose-escalation part were adverse events (AEs) and dose-limiting toxicities (DLTs), and those for the dose-expansion part were confirmed best overall response (BOR) per investigator (Response Evaluation Criteria in Solid Tumors V.1.1) and safety. The dose-expansion part followed a two-stage design; 16 patients were enrolled and treated in stage 1 (single-arm part). A futility analysis based on BOR was planned to determine whether stage 2 (randomized controlled part) would be initiated. RESULTS: At data cut-off, 36 patients had received M9241 plus avelumab in the dose-escalation part. All DLs were well tolerated; one DLT occurred at DL3 (grade 3 autoimmune hepatitis). The maximum-tolerated dose was not reached, and DL5 was declared the recommended phase II dose, considering an observed drug-drug interaction at DL4. Two patients with advanced bladder cancer (DL2 and DL4) had prolonged complete responses. In the dose-expansion part, no objective responses were recorded in the 16 patients with advanced UC; the study failed to meet the criterion (≥3 confirmed objective responses) to initiate stage 2. Any-grade treatment-related AEs occurred in 15 patients (93.8%), including grade ≥3 in 8 (50.0%); no treatment-related deaths occurred. Exposures for avelumab and M9241 concentrations were within expected ranges. CONCLUSIONS: M9241 plus avelumab was well tolerated at all DLs, including the dose-expansion part, with no new safety signals. However, the dose-expansion part did not meet the predefined efficacy criterion to proceed to stage 2.