Maveropepimut-S, a DPX-Based Immune-Educating Therapy, Shows Promising and Durable Clinical Benefit in Patients with Recurrent Ovarian Cancer, a Phase II Trial.

PURPOSE: Patients with platinum-resistant ovarian cancer respond poorly to existing therapies. Hence there is a need for more effective treatments. PATIENTS AND METHODS: The DeCidE1 trial is a multicenter, randomized, open-label, single-arm phase II study to evaluate the safety and effectiveness of maveropepimut-S with cyclophosphamide in patients with recurrent ovarian cancer. Median follow-up for evaluable subjects was 4.4 months. Data were collected from March 2019 to June 2021. Subjects received two injections of 0.25 mL maveropepimut-S 3 weeks apart, followed by one 0.1-mL doses, every 8 weeks up to progression. Oral cyclophosphamide, 50 mg twice daily, was administered in repeating weekly on and off cycles. RESULTS: Twenty-two patients were enrolled. Median age was 58 years (38-78 years). Among the evaluable population, the objective response rate (ORR) was 21% [90% confidence interval (CI), 7.5%-41.9%], with a disease control rate (DCR) of 63% (90% CI, 41.8%-81.3%), including 4 (21%) patients with partial responses, 8 (42%) stable disease, and 7 (37%) progressive disease. The ORRs were consistent across subgroups based on platinum sensitivity, and DCR was higher in the platinum-resistant subpopulation. Four SD patients maintained clinical benefit up to 25 months. Most treatment-related adverse events (TRAE) were grade 1 and 2 (87% of unique events). Most common AEs were injection site reactions. Eight subjects reported grade 3 and no grade 4 AEs. Survivin-specific T-cell responses were observed in treated patients with clinical benefit. CONCLUSIONS: Maveropepimut-S with intermittent low-dose cyclophosphamide is well-tolerated, with clinical benefit for patients with recurrent ovarian cancer. Observed responses are irrespective of the platinum status.

A novel TNFR2 agonist antibody expands highly potent regulatory T cells.

Regulatory T cells (Treg cells) restrict immune system activity, such as in response to self-antigens, and are switched on by tumor necrosis factor receptor 2 (TNFR2). Therapeutic activation of TNFR2, thereby expanding Treg cells and suppressing immune activity, may be beneficial to patients with various inflammatory diseases. Here, we characterized a new human TNFR2-directed antibody agonist isolated from mice. We found that the antibody agonist expanded the number of Treg cells within cultures of primary human CD4+ T cells from healthy donors and patients with type 1 diabetes or Sézary syndrome. These Treg cells had increased metabolic gene expression and intracellular itaconate concentrations, characteristics associated with maximally suppressive, anti-inflammatory Treg cells. Furthermore, antibody-expanded Treg cells repressed the activity of primary human CD8+ effector T cells (Teff cells). Epitope mapping suggested that the antibody bound to TNFR2 through a natural cross-linking surface and that Treg cell expansion was independent of the antibody Fc region. In addition, Treg cell expansion was not increased by adding either supplemental TNF ligand or a cross-linking reagent, suggesting that the antibody agonist by itself can elicit maximal activity, a notion that was confirmed by increased secretion of soluble TNFR2. Pending in vivo tests, these features indicate that this TNFR2 antibody agonist has the potential to safely and effectively treat various inflammatory disorders.

Evaluation of the protective potential of antibody and T cell responses elicited by a novel preventative vaccine towards respiratory syncytial virus small hydrophobic protein.

The small hydrophobic (SH) glycoprotein of human respiratory syncytial virus (RSV) is a transmembrane protein that is poorly accessible by antibodies on the virion but has an ectodomain (SHe) that is accessible and expressed on infected cells. The SHe from RSV strain A has been formulated in DPX, a unique delivery platform containing an adjuvant, and is being evaluated as an RSV vaccine candidate. The proposed mechanism of protection is the immune-mediated clearance of infected cells rather than neutralization of the virion. Our phase I clinical trial data clearly showed that vaccination resulted in robust antibody responses, but it was unclear if these immune responses have any correlation to immune responses to natural infection with RSV. Therefore, we embarked on this study to examine these immune responses in older adults with confirmed RSV infection. We compared vaccine-induced (DPX-RSV(A)) immune responses from participants in a Phase 1 clinical trial to paired acute and convalescent titers from older adults with symptomatic laboratory-confirmed RSV infection. Serum samples were tested for anti-SHe IgG titers and the isotypes determined. T cell responses were evaluated by IFN-γ ELISPOT. Anti-SHe titers were detected in 8 of 42 (19%) in the acute phase and 16 of 42 (38%) of convalescent serum samples. IgG1, IgG3, and IgA were the prevalent isotypes generated by both vaccination and infection. Antigen-specific T cell responses were detected in 9 of 16 (56%) of vaccinated participants. Depletion of CD4+ but not CD8+ T cells abrogated the IFN-γ ELISPOT response supporting the involvement of CD4+ T cells in the immune response to vaccination. The data showed that an immune response like that induced by DPX-RSV(A) could be seen in a subset of participants with confirmed RSV infection. These findings show that older adults with clinically significant infection as well as vaccinated adults generate a humoral response to SHe. The induction of both SHe-specific antibody and cellular responses support further clinical development of the DPX-RSV(A) vaccine.

Optimizing TNFR2 antagonism for immunotherapy with tumor microenvironment specificity.

Most approved cancer immunotherapies lack T-regulatory (Treg) or tumor specificity. TNF receptor 2 (TNFR2) antibody antagonism is emerging as an attractive immunotherapy due to its tumor microenvironment (TME) specificity. Here we show that the human TNFR2 receptor is overexpressed on both human tumor cells and on human tumor-residing Tregs, but negligibly expressed on beneficial T effectors (Teffs). Further, we found widespread, if variable, TNFR2 expression on 788 human tumor cell lines from diverse cancer tissues. These findings provided strong rationale for developing a targeted immunotherapy using a TNFR2 antibody antagonist. We designed a novel, human-directed TNFR2 antibody antagonist and tested it for function using three cell-based TME assays. The antagonist showed TME specificity by killing of TNFR2-expressing tumor cells and Tregs, but sparing Teffs, which proliferated. However, the antagonist shuffled between five isoforms, only one of which showed the desirable function. We designed and tested several new chimeric human versions of the antagonist, finding that the IgG2 isotype functioned better than the IgG1 isotype. To further improve function, we introduced targeted mutations to its amino acid sequence to stabilize the natural variability of the IgG2 isotype's hinge. Altogether, our findings suggest that optimal TNFR2 antagonists are of the human IgG2 isotype, have hinge stabilization, and have wide separation of antibody arms to bind to newly synthesized TNFR2 on rapidly growing tumor cells. Antagonistic antibodies with these characteristics, when bound to TNFR2, can form a nonsignaling cell surface dimer that functions with high TME specificity.

Targeting TNFR2 with antagonistic antibodies inhibits proliferation of ovarian cancer cells and tumor-associated Tregs.

Major barriers to cancer therapy include the lack of selective inhibitors of regulatory T cells (Tregs) and the lack of broadly applicable ways to directly target tumors through frequently expressed surface oncogenes. Tumor necrosis factor receptor 2 (TNFR2) is an attractive target protein because of its restricted abundance to highly immunosuppressive Tregs and oncogenic presence on human tumors. We characterized the effect of TNFR2 inhibition using antagonistic antibodies. In culture-based assays, we found that two TNFR2 antagonists inhibited Treg proliferation, reduced soluble TNFR2 secretion from normal cells, and enabled T effector cell expansion. The antagonistic activity occurred in the presence of added TNF, a natural TNFR2 agonist. These TNFR2 antibodies killed Tregs isolated from ovarian cancer ascites more potently than it killed Tregs from healthy donor samples, suggesting that these antibodies may have specificity for the tumor microenvironment. The TNFR2 antagonists also killed OVCAR3 ovarian cancer cells, which have abundant surface TNFR2. The antibodies stabilized antiparallel dimers in cell surface TNFR2 that rendered the receptor unable to activate the nuclear factor κB pathway and trigger cell proliferation. Our data suggest that, by targeting tumor cells and immunosuppressive tumor-associated Tregs, antagonistic TNFR2 antibodies may be an effective treatment for cancers positive for TNFR2.

Treg activation defect in type 1 diabetes: correction with TNFR2 agonism.

Activated T-regulatory cells (aTregs) prevent or halt various forms of autoimmunity. We show that type 1 diabetics (T1D) have a Treg activation defect through an increase in resting Tregs (rTregs, CD4(+)CD25(+)Foxp3(+)CD45RA) and decrease in aTregs (CD4(+)CD25(+)Foxp3(+)CD45RO) (n= 55 T1D, n=45 controls, P=0.01). The activation defect persists life long in T1D subjects (T1D=45, controls=45, P=0.01, P=0.04). Lower numbers of aTregs had clinical significance because they were associated with a trend for less residual C-peptide secretion from the pancreas (P=0.08), and poorer HbA1C control (P=0.03). In humans, the tumor necrosis factor receptor 2 (TNFR2) is obligatory for Treg induction, maintenance and expansion of aTregs. TNFR2 agonism is a method for stimulating Treg conversion from resting to activated. Using two separate in vitro expansion protocols, TNFR2 agonism corrected the T1D activation defect by triggering conversion of rTregs into aTregs (n=54 T1D, P<0.001). TNFR2 agonism was superior to standard protocols and TNF in proliferating Tregs. In T1D, TNFR2 agonist-expanded Tregs were homogeneous and functionally potent by virtue of suppressing autologous cytotoxic T cells in a dose-dependent manner comparable to controls. Targeting the TNFR2 receptor for Treg expansion in vitro demonstrates a means to correct the activation defect in T1D.

High Persister Mutants in Mycobacterium tuberculosis.

Mycobacterium tuberculosis forms drug-tolerant persister cells that are the probable cause of its recalcitrance to antibiotic therapy. While genetically identical to the rest of the population, persisters are dormant, which protects them from killing by bactericidal antibiotics. The mechanism of persister formation in M. tuberculosis is not well understood. In this study, we selected for high persister (hip) mutants and characterized them by whole genome sequencing and transcriptome analysis. In parallel, we identified and characterized clinical isolates that naturally produce high levels of persisters. We compared the hip mutants obtained in vitro with clinical isolates to identify candidate persister genes. Genes involved in lipid biosynthesis, carbon metabolism, toxin-antitoxin systems, and transcriptional regulators were among those identified. We also found that clinical hip isolates exhibited greater ex vivo survival than the low persister isolates. Our data suggest that M. tuberculosis persister formation involves multiple pathways, and hip mutants may contribute to the recalcitrance of the infection.

Lassomycin, a ribosomally synthesized cyclic peptide, kills mycobacterium tuberculosis by targeting the ATP-dependent protease ClpC1P1P2.

Languishing antibiotic discovery and flourishing antibiotic resistance have prompted the development of alternative untapped sources for antibiotic discovery, including previously uncultured bacteria. Here, we screen extracts from uncultured species against Mycobacterium tuberculosis and identify lassomycin, an antibiotic that exhibits potent bactericidal activity against both growing and dormant mycobacteria, including drug-resistant forms of M. tuberculosis, but little activity against other bacteria or mammalian cells. Lassomycin is a highly basic, ribosomally encoded cyclic peptide with an unusual structural fold that only partially resembles that of other lasso peptides. We show that lassomycin binds to a highly acidic region of the ClpC1 ATPase complex and markedly stimulates its ATPase activity without stimulating ClpP1P2-catalyzed protein breakdown, which is essential for viability of mycobacteria. This mechanism, uncoupling ATPase from proteolytic activity, accounts for the bactericidal activity of lassomycin.