Autologous human preclinical modeling of melanoma interpatient clinical responses to immunotherapeutics.

BACKGROUND: Despite recent advances in immunotherapy, a substantial population of late-stage melanoma patients still fail to achieve sustained clinical benefit. Lack of translational preclinical models continues to be a major challenge in the field of immunotherapy; thus, more optimized translational models could strongly influence clinical trial development. To address this unmet need, we designed a preclinical model reflecting the heterogeneity in melanoma patients' clinical responses that can be used to evaluate novel immunotherapies and synergistic combinatorial treatment strategies. Using our all-autologous humanized melanoma mouse model, we examined the efficacy of a novel engineered interleukin 2 (IL-2)-based cytokine variant immunotherapy. METHODS: To study immune responses and antitumor efficacy for human melanoma tumors, we developed an all-autologous humanized melanoma mouse model using clinically annotated, matched patient tumor cells and peripheral blood mononuclear cells (PBMCs). After inoculating immunodeficient NSG mice with patient tumors and an adoptive cell transfer of autologous PBMCs, mice were treated with anti-PD-1, a novel investigational engineered IL-2-based cytokine (nemvaleukin), or recombinant human IL-2 (rhIL-2). The pharmacodynamic effects and antitumor efficacy of these treatments were then evaluated. We used tumor cells and autologous PBMCs from patients with varying immunotherapy responses to both model the diversity of immunotherapy efficacy observed in the clinical setting and to recapitulate the heterogeneous nature of melanoma. RESULTS: Our model exhibited long-term survival of engrafted human PBMCs without developing graft-versus-host disease. Administration of an anti-PD-1 or nemvaleukin elicited antitumor responses in our model that were patient-specific and were found to parallel clinical responsiveness to checkpoint inhibitors. An evaluation of nemvaleukin-treated mice demonstrated increased tumor-infiltrating CD4+ and CD8+ T cells, preferential expansion of non-regulatory T cell subsets in the spleen, and significant delays in tumor growth compared with vehicle-treated controls or mice treated with rhIL-2. CONCLUSIONS: Our model reproduces differential effects of immunotherapy in melanoma patients, capturing the inherent heterogeneity in clinical responses. Taken together, these data demonstrate our model's translatability for novel immunotherapies in melanoma patients. The data are also supportive for the continued clinical investigation of nemvaleukin as a novel immunotherapeutic for the treatment of melanoma.

Nemvaleukin alfa, a novel engineered IL-2 fusion protein, drives antitumor immunity and inhibits tumor growth in small cell lung cancer.

BACKGROUND: Small cell lung cancer (SCLC) is a deadly disease with a 5-year survival of less than 7%. The addition of immunotherapy to chemotherapy was recently approved as first-line treatment; however, the improved clinical benefit is modest, highlighting an urgent need for new treatment strategies. Nemvaleukin alfa, a novel engineered interleukin-2 fusion protein currently in phase I-III studies, is designed to selectively expand cytotoxic natural killer (NK) cells and CD8+ T cells. Here, using a novel SCLC murine model, we investigated the effects of a mouse version of nemvaleukin (mNemvaleukin) on tumor growth and antitumor immunity. METHODS: A novel Rb1 -/- p53 -/- p130 -/- SCLC model that mimics human disease was generated. After confirming tumor burden by MRI, mice were randomized into four treatment groups: vehicle, mNemvaleukin alone, chemotherapy (cisplatin+etoposide) alone, or the combination of mNemvaleukin and chemotherapy. Tumor growth was measured by MRI and survival was recorded. Tumor-infiltrating lymphocytes and peripheral blood immune cells were analyzed by flow cytometry. Cytokine and chemokine secretion were quantified and transcriptomic analysis was performed to characterize the immune gene signatures. RESULTS: mNemvaleukin significantly inhibited SCLC tumor growth, which was further enhanced by the addition of chemotherapy. Combining mNemvaleukin with chemotherapy provided the most significant survival benefit. Profiling of tumor-infiltrating lymphocytes revealed mNemvaleukin expanded the total number of tumor-infiltrating NK and CD8+ T cells. Furthermore, mNemvaleukin increased the frequencies of activated and proliferating NK and CD8+ T cells in tumors. Similar immune alterations were observed in the peripheral blood of mNemvaleukin-treated mice. Of note, combining mNemvaleukin with chemotherapy had the strongest effects in activating effector and cytotoxic CD8+ T cells. mNemvaleukin alone, and in combination with chemotherapy, promoted proinflammatory cytokine and chemokine production, which was further confirmed by transcriptomic analysis. CONCLUSIONS: mNemvaleukin, a novel cytokine-based immunotherapy, significantly inhibited murine SCLC tumor growth and prolonged survival, which was further enhanced by the addition of chemotherapy. mNemvaleukin alone, and in combination with chemotherapy, drove a strong antitumor immune program elicited by cytotoxic immune cells. Our findings support the evaluation of nemvaleukin alone or in combination with chemotherapy in clinical trials for the treatment of SCLC.

Pharmacokinetics and Pharmacodynamic Effects of Nemvaleukin Alfa, a Selective Agonist of the Intermediate-Affinity IL-2 Receptor, in Cynomolgus Monkeys.

Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel cytokine created by the fusion of circularly permuted interleukin-2 (IL-2) to the IL-2Rα subunit of the IL-2 receptor (IL-2R) complex that confers selectivity for the intermediate-affinity IL-2R expressed on CD8+ T cells and natural killer (NK) cells. The pharmacokinetics and selective pharmacodynamic properties of nemvaleukin have been demonstrated using in vitro and in vivo mouse models. The pharmacokinetic/pharmacodynamic effects of nemvaleukin on immune cell subtypes were evaluated in cynomolgus monkeys after intravenous and subcutaneous administration to inform dose selection and predict pharmacodynamic effects in humans. Male drug-naïve cynomolgus monkeys (N = 15) were administered either single-dose (0.3 mg/kg i.v.; 0.3 mg/kg or 1.0 mg/kg s.c.) or repeated doses (0.1 mg/kg i.v. on days 1-5 or 0.5 mg/kg s.c. on days 1 and 4) of nemvaleukin. Serial blood samples were collected for pharmacokinetic assessment, immunophenotyping by flow cytometry, and profiling of serum cytokines. Repeat-dose subcutaneous administration of nemvaleukin with less frequent dosing resulted in total systemic exposure and trough serum concentrations comparable to those seen with intravenous administration, with lower peak serum concentrations. Transient elevation of interferon-γ and IL-6 peaked at 2 and 8 hours after intravenous and subcutaneous administration, respectively. Selective expansion of immunoprotective central memory, effector memory, terminal effector CD8+ T cells, and CD56+ NK cells, and minimal expansion of immunosuppressive CD4+CD25+FoxP3+ regulatory T cells was observed after both intravenous and subcutaneous administration. These data support the ongoing clinical evaluation of intravenous and subcutaneous nemvaleukin. SIGNIFICANCE STATEMENT: Administration of the novel interleukin-2 receptor agonist nemvaleukin alfa to cynomolgus monkeys resulted in selective expansion of immune effector cells, including CD8+ T and natural killer cells with minimal effects on immunosuppressive CD4+ regulatory T cells, confirming the design of nemvaleukin and highlighting its potential as a cancer immunotherapy. Subcutaneous administration of nemvaleukin achieved systemic exposure and immunostimulatory effects similar to those observed after more frequent intravenous dosing and may represent a practical alternative in a clinical setting.

ALKS 4230: a novel engineered IL-2 fusion protein with an improved cellular selectivity profile for cancer immunotherapy.

BACKGROUND: Interleukin-2 (IL-2) plays a pivotal role in immune homeostasis due to its ability to stimulate numerous lymphocyte subsets including natural killer (NK) cells, effector CD4+ and CD8+ T cells, and regulatory T cells (Tregs). Low concentrations of IL-2 induce signaling through the high-affinity IL-2 receptor (IL-2R) comprised of IL-2Rα, IL-2Rß, and common γ chain (γc), preferentially expressed on Tregs. Higher concentrations of IL-2 are necessary to induce signaling through the intermediate-affinity IL-2R, composed of IL-2Rß and γc, expressed on memory CD8+ T cells and NK cells. Recombinant human IL-2 (rhIL-2) is approved for treatment of metastatic melanoma and renal cell carcinoma (RCC), but adverse events including capillary leak syndrome, potentially mediated through interaction with the high-affinity IL-2R, limit its therapeutic use. Furthermore, antitumor efficacy of IL-2 may also be limited by preferential expansion of immunosuppressive Tregs. ALKS 4230 is an engineered fusion protein comprised of a circularly-permuted IL-2 with the extracellular domain of IL-2Rα, designed to selectively activate effector lymphocytes bearing the intermediate-affinity IL-2R. RESULTS: ALKS 4230 was equipotent to rhIL-2 in activating human cells bearing the intermediate-affinity IL-2R, and less potent than rhIL-2 on cells bearing the high-affinity IL-2R. As observed in vitro with primary human cells from healthy donors and advanced cancer patients, ALKS 4230 induced greater activation and expansion of NK cells with reduced expansion of Tregs relative to rhIL-2. Similarly, in mice, ALKS 4230 treatment stimulated greater expansion of NK cells and memory-phenotype CD8+ T cells at doses that did not expand or activate Tregs. ALKS 4230 treatment induced significantly lower levels of proinflammatory cytokines, including tumor necrosis factor alpha, interleukin-6, and interferon gamma relative to rhIL-2. Furthermore, ALKS 4230 exhibited superior antitumor efficacy in the mouse B16F10 lung tumor model, where ALKS 4230 could be administered via multiple routes of administration and dosing schedules while achieving equivalent antitumor efficacy. CONCLUSIONS: ALKS 4230 exhibited enhanced pharmacokinetic and selective pharmacodynamic properties resulting in both improved antitumor efficacy and lower indices of toxicity relative to rhIL-2 in mice. These data highlight the potential of ALKS 4230 as a novel cancer immunotherapy, and as such, the molecule is being evaluated clinically.

Crystal structure of Staphylococcus aureus tRNA adenosine deaminase TadA in complex with RNA.

Bacterial tRNA adenosine deaminases (TadAs) catalyze the hydrolytic deamination of adenosine to inosine at the wobble position of tRNA(Arg2), a process that enables this single tRNA to recognize three different arginine codons in mRNA. In addition, inosine is also introduced at the wobble position of multiple eukaryotic tRNAs. The genes encoding these deaminases are essential in bacteria and yeast, demonstrating the importance of their biological activity. Here we report the crystallization and structure determination to 2.0 A of Staphylococcus aureus TadA bound to the anticodon stem-loop of tRNA(Arg2) bearing nebularine, a non-hydrolyzable adenosine analog, at the wobble position. The cocrystal structure reveals the basis for both sequence and structure specificity in the interactions of TadA with RNA, and it additionally provides insight into the active site architecture that promotes efficient hydrolytic deamination.

Crystal structure of vancosaminyltransferase GtfD from the vancomycin biosynthetic pathway: interactions with acceptor and nucleotide ligands.

The TDP-vancosaminyltransferase GtfD catalyzes the attachment of L-vancosamine to a monoglucosylated heptapeptide intermediate during the final stage of vancomycin biosynthesis. Glycosyltransferases from this and similar antibiotic pathways are potential tools for the design of new compounds that are effective against vancomycin resistant bacterial strains. We have determined the X-ray crystal structure of GtfD as a complex with TDP and the natural glycopeptide substrate at 2.0 A resolution. GtfD, a member of the bidomain GT-B glycosyltransferase superfamily, binds TDP in the interdomain cleft, while the aglycone acceptor binds in a deep crevice in the N-terminal domain. However, the two domains are more interdependent in terms of substrate binding and overall structure than was evident in the structures of closely related glycosyltransferases GtfA and GtfB. Structural and kinetic analyses support the identification of Asp13 as a catalytic general base, with a possible secondary role for Thr10. Several residues have also been identified as being involved in donor sugar binding and recognition.

Structure of the TDP-epi-vancosaminyltransferase GtfA from the chloroeremomycin biosynthetic pathway.

During the biosynthesis of the vancomycin-class antibiotic chloroeremomycin, TDP-epi-vancosaminyltransferase GtfA catalyzes the attachment of 4-epi-vancosamine from a TDP donor to the beta-OHTyr-6 of the aglycone cosubstrate. Glycosyltransferases from this pathway are potential tools for the combinatorial design of new antibiotics that are effective against vancomycin-resistant bacterial strains. These enzymes are members of the GT-B glycosyltransferase superfamily, which share a homologous bidomain topology. We present the 2.8-A crystal structures of GtfA complexes with vancomycin and the natural monoglycosylated peptide substrate, representing the first direct observation of acceptor substrate binding among closely related glycosyltransferases. The acceptor substrates bind to the N-terminal domain such that the aglycone substrate's reactive hydroxyl group hydrogen bonds to the side chains of Ser-10 and Asp-13, thus identifying these as residues of potential catalytic importance. As well as an open form of the enzyme, the crystal structures have revealed a closed form in which a TDP ligand is bound at a donor substrate site in the interdomain cleft, thereby illustrating not only binding interactions, but the conformational changes in the enzyme that accompany substrate binding.

Incorporation of glucose analogs by GtfE and GtfD from the vancomycin biosynthetic pathway to generate variant glycopeptides.

Analogs of the glycopeptide antibiotics vancomycin and teicoplanin with alterations in one or both sugar moieties of the disaccharide have been prepared by tandem action of the vancomycin pathway glycosyltransferases GtfE and GtfD. All four regioisomers (2-, 3-, 4-, 6-) of TDP-deoxyglucoses and UDP/TDP-aminoglucoses were prepared, predominantly by action of D-glucopyranosyl-1-phosphate thymidylyltransferase, E(p). GtfE transferred the deoxyglucoses or aminoglucoses onto the 4-OH of 4-hydroxyphenylglycine of both the vancomycin and teicoplanin aglycone scaffolds. Kinetic analysis indicated the 2-, 3-, 4-, and 6-amino-glucoses were transferred by GtfE with only a 4- to 30-fold drop in k(cat) and no effect on K(m) compared to the native substrate, UDP/TDP-glucose, suggesting preparative utility. The next enzyme, GtfD, could utilize the variant glucosyl-peptides as substrates for transfer of L-4-epi-vancosamine. The aminosugar moieties in these variant glycopeptides introduce sites for acylation or reductive alkylation.

The structural basis for induction of VanB resistance.

Because teicoplanin and vancomycin are the last line of defense for many bacterial infections, the emergence of resistance to glycopeptide antibiotics in enterococci and streptococci has aroused concern. Despite their similarity in terms of structure and mechanism of action, vancomycin induces the expression of genes that leads to bacterial resistance, and teicoplanin does not. We have used a combination of chemical and enzymatic methods to produce sets of vancomycin and teicoplanin analogues that allow us to consider whether the aglycon, the carbohydrate, or other parts of these molecules stimulate VanB resistance. We show that the teicoplanin and vancomycin aglycons are the structural elements that lead to induction of resistance. We think that lipid-containing analogues of vancomycin, like teicoplanin itself, circumvent resistance because the lipid chain changes the periplasmic distribution of the glycopeptide and, therefore, changes the biosynthetic step that it blocks.

Purification, crystallization and preliminary structural studies of dTDP-4-keto-6-deoxy-glucose-5-epimerase (EvaD) from Amycolatopsis orientalis, the fourth enzyme in the dTDP-L-epivancosamine biosynthetic pathway.

The vancomycin class of antibiotics is regarded as the last line of defence against Gram-positive bacteria. The compounds used clinically are very complex organic molecules and are made by fermentation. The biosynthesis of these is complex and fascinating. Its study holds out the prospect of utilizing genetic engineering of the enzymes in the pathway in order to produce novel vancomycin analogues. In part, this requires detailed structural insight into substrate specificity as well as the enzyme mechanism. The crystallization of one of the enzymes in the chloroeremomycin biosynthetic pathway (a member of the vancomycin family), dTDP-3-amino-4-keto 2,3,6-trideoxy-3-C-methyl-glucose-5-epimerase (EvaD) from Amycolatopsis orientalis, is reported here. The protein is fourth in the pathway which makes a carbohydrate essential for the activity of chloroeremomycin. The crystals of EvaD diffract to 1.5 A and have unit-cell parameters a = 98.6, b = 72.0, c = 57.1 A with space group P2(1)2(1)2. Data to this resolution were collected at the European Synchrotron Radiation Facility.