Diastereoselective nickel-catalyzed reductive coupling of alkynes and aldehydes and application towards the B-type amphidinolides

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006.Vita.Includes bibliographical references.The application of recently developed stereoselective nickel-catalyzed reductive coupling reactions of alkynes and aldehydes to the synthesis of complex natural product targets was explored. The "B-Type" amphidinolides were selected as ideal targets owing to their molecular complexity and the paucity of synthetically viable means for their total construction. The diastereoselective nickel-catalyzed reductive coupling of simple aryl-substituted alkynes and a-oxyaldehydes was developed and applied to the construction of the C15-C26 region of amphidinolide H3. ... Alternatively, the nickel-catalyzed reductive coupling reaction of 1,3-enynes and aldehydes was found to be a very effective way of installing the congested 1,3-diene moiety common to all members of this class of natural products. This methodology was further examined as a fragment coupling strategy for the syntheses of amphidinolides G3 and H4. This allowed for a highly convergent and functional group tolerant assembly of these ... molecules and, to date, stands as the most complicated setting for the application of the catalytic reductive coupling reaction.by Chudi O. Ndubaku.Ph.D

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Bio-inspired synthesis of xishacorenes A, B, and C, and a new congener from fuscol.

The xishacorene natural products are structurally unique apolar diterpenoids that feature a bicyclo[3.3.1] framework. These secondary metabolites likely arise from the well-studied, structurally related diterpenoid fuscol. In this manuscript, we describe the conversion of fuscol to xishacorenes A, B, and C, as well as a previously unreported congener, which we have named xishacorene D. In addition, we describe immunomodulatory activity studies of the xishacorenes, a structurally related analogue, and fuscol. These studies were aided by an accurate determination of the physical properties (e.g., molar extinction coefficient) of the highly apolar xishacorenes

Synergy of a STING agonist and an IL-2 superkine in cancer immunotherapy against MHC I-deficient and MHC I+ tumors.

Cyclic dinucleotides (CDN) and Toll-like receptor (TLR) ligands mobilize antitumor responses by natural killer (NK) cells and T cells, potentially serving as complementary therapies to immune checkpoint therapy. In the clinic thus far, however, CDN therapy targeting stimulator of interferon genes (STING) protein has yielded mixed results, perhaps because it initiates responses potently but does not provide signals to sustain activation and proliferation of activated cytotoxic lymphocytes. To improve efficacy, we combined CDN with a half life-extended interleukin-2 (IL-2) superkine, H9-MSA (mouse serum albumin). CDN/H9-MSA therapy induced dramatic long-term remissions of the most difficult to treat major histocompatibility complex class I (MHC I)–deficient and MHC I+ tumor transplant models. H9-MSA combined with CpG oligonucleotide also induced potent responses. Mechanistically, tumor elimination required CD8 T cells and not NK cells in the case of MHC I+ tumors and NK cells but not CD8 T cells in the case of MHC-deficient tumors. Furthermore, combination therapy resulted in more prolonged and more intense NK cell activation, cytotoxicity, and expression of cytotoxic effector molecules in comparison with monotherapy. Remarkably, in a primary autochthonous sarcoma model that is refractory to PD-1 checkpoint therapy, the combination of CDN/H9-MSA with checkpoint therapy yielded long-term remissions in the majority of the animals, mediated by T cells and NK cells. This combination therapy has the potential to activate responses in tumors resistant to current therapies and prevent MHC I loss accompanying acquired resistance of tumors to checkpoint therapy

NK cells mediate clearance of CD8+ T cell–resistant tumors in response to STING agonists

Several immunotherapy approaches that mobilize CD8+ T cell responses stimulate tumor rejection, and some, such as checkpoint blockade, have been approved for several cancer indications and show impressive increases in patient survival. However, tumors may evade CD8+ T cell recognition via loss of MHC molecules or because they contain few or no neoantigens. Therefore, approaches are needed to combat CD8+ T cell-resistant cancers. STING-activating cyclic dinucleotides (CDNs) are a new class of immune-stimulating agents that elicit impressive CD8+ T cell-mediated tumor rejection in preclinical tumor models and are now being tested in clinical trials. Here, we demonstrate powerful CDN-induced, natural killer (NK) cell-mediated tumor rejection in numerous tumor models, independent of CD8+ T cells. CDNs enhanced NK cell activation, cytotoxicity, and antitumor effects in part by inducing type I interferon (IFN). IFN acted in part directly on NK cells in vivo and in part indirectly via the induction of IL-15 and IL-15 receptors, which were important for CDN-induced NK activation and tumor control. After in vivo administration of CDNs, dendritic cells (DCs) up-regulated IL-15Rα in an IFN-dependent manner. Mice lacking the type I IFN receptor specifically on DCs had reduced NK cell activation and tumor control. Therapeutics that activate NK cells, such as CDNs, checkpoint inhibitors, NK cell engagers, and cytokines, may represent next-generation approaches to cancer immunotherapy

Magnitude of Therapeutic STING Activation Determines CD8⁺ T Cell-Mediated Anti-tumor Immunity

STING pathway activation by intratumoral administration of cyclic dinucleotides (CDNs) results in stable tumor regression, yet the underlying innate and adaptive immune mechanisms are not fully established. ADU-S100, CDN under clinical evaluation, was used with an optimized dosing regimen to uncover key immune requirements for tumor regression. An immunogenic dose induces local expansion of tumor-specific CD8+ T cells, which are both necessary and sufficient for durable anti-tumor immunity and correlated with STING activation in hematopoietic but not tumor or stromal cells. Type I IFN, but not TNFα, drives optimal anti-tumor immune responses. The function of ADU-S100-induced CD8+ T cells was enhanced by combination with immune checkpoint modulators anti-PD-1 and anti-CTLA4. These results provide fundamental mechanistic insights into STING IT therapy

Discovery of Small-Molecule Inhibitors of Ubiquitin Specific Protease 7 (USP7) Using Integrated NMR and in Silico Techniques

USP7 is a deubiquitinase implicated in destabilizing the tumor suppressor p53, and for this reason it has gained increasing attention as a potential oncology target for small molecule inhibitors. Herein we describe the biophysical, biochemical, and computational approaches that led to the identification of 4-(2-aminopyridin-3-yl)­phenol compounds described by Kategaya (Nature 2017, 550, 534–538) as specific inhibitors of USP7. Fragment based lead discovery (FBLD) by NMR combined with virtual screening and re-mining of biochemical high-throughput screening (HTS) hits led to the discovery of a series of ligands that bind in the “palm” region of the catalytic domain of USP7 and inhibit its catalytic activity. These ligands were then optimized by structure-based design to yield cell-active molecules with reasonable physical properties. This discovery process not only involved multiple techniques working in concert but also illustrated a unique way in which hits from orthogonal screening approaches complemented each other for lead identification

Discovery of Small-Molecule Inhibitors of Ubiquitin Specific Protease 7 (USP7) Using Integrated NMR and in Silico Techniques

USP7 is a deubiquitinase implicated in destabilizing the tumor suppressor p53, and for this reason it has gained increasing attention as a potential oncology target for small molecule inhibitors. Herein we describe the biophysical, biochemical, and computational approaches that led to the identification of 4-(2-aminopyridin-3-yl)­phenol compounds described by Kategaya (Nature 2017, 550, 534–538) as specific inhibitors of USP7. Fragment based lead discovery (FBLD) by NMR combined with virtual screening and re-mining of biochemical high-throughput screening (HTS) hits led to the discovery of a series of ligands that bind in the “palm” region of the catalytic domain of USP7 and inhibit its catalytic activity. These ligands were then optimized by structure-based design to yield cell-active molecules with reasonable physical properties. This discovery process not only involved multiple techniques working in concert but also illustrated a unique way in which hits from orthogonal screening approaches complemented each other for lead identification