Open drug discovery in Alzheimer\u27s disease.

Alzheimer\u27s disease (AD) drug discovery has focused on a set of highly studied therapeutic hypotheses, with limited success. The heterogeneous nature of AD processes suggests that a more diverse, systems-integrated strategy may identify new therapeutic hypotheses. Although many target hypotheses have arisen from systems-level modeling of human disease, in practice and for many reasons, it has proven challenging to translate them into drug discovery pipelines. First, many hypotheses implicate protein targets and/or biological mechanisms that are under-studied, meaning there is a paucity of evidence to inform experimental strategies as well as high-quality reagents to perform them. Second, systems-level targets are predicted to act in concert, requiring adaptations in how we characterize new drug targets. Here we posit that the development and open distribution of high-quality experimental reagents and informatic outputs-termed target enabling packages (TEPs)-will catalyze rapid evaluation of emerging systems-integrated targets in AD by enabling parallel, independent, and unencumbered research

Discovery of FERM domain protein-protein interaction inhibitors for MSN and CD44 as a potential therapeutic approach for Alzheimer\u27s disease.

Proteomic studies have identified moesin (MSN), a protein containing a four-point-one, ezrin, radixin, moesin (FERM) domain, and the receptor CD44 as hub proteins found within a coexpression module strongly linked to Alzheimer\u27s disease (AD) traits and microglia. These proteins are more abundant in Alzheimer\u27s patient brains, and their levels are positively correlated with cognitive decline, amyloid plaque deposition, and neurofibrillary tangle burden. The MSN FERM domain interacts with the phospholipid phosphatidylinositol 4,5-bisphosphate (PI

Pretargeted Radioimmunotherapy Using Genetically Engineered Antibody-Streptavidin Fusion Proteins for Treatment of Non-Hodgkin Lymphoma

Pretargeted radioimmunotherapy (PRIT) using streptavidin (SAv)-biotin technology can deliver higher therapeutic doses of radioactivity to tumors than conventional RIT. However, “endogenous” biotin can interfere with the effectiveness of this approach by blocking binding of radiolabeled biotin to SAv. We engineered a series of SAv FPs that down-modulate the affinity of SAv for biotin, while retaining high avidity for divalent DOTA-bis-biotin to circumvent this problem

Discovery and characterization of a specific inhibitor of serine-threonine kinase cyclin-dependent kinase-like 5 (CDKL5) demonstrates role in hippocampal CA1 physiology

Pathological loss-of-function mutations in cyclin-dependent kinase-like 5 (CDKL5) cause CDKL5 deficiency disorder (CDD), a rare and severe neurodevelopmental disorder associated with severe and medically refractory early-life epilepsy, motor, cognitive, visual, and autonomic disturbances in the absence of any structural brain pathology. Analysis of genetic variants in CDD has indicated that CDKL5 kinase function is central to disease pathology. CDKL5 encodes a serine-threonine kinase with significant homology to GSK3β, which has also been linked to synaptic function. Further, Cdkl5 knock-out rodents have increased GSK3β activity and often increased long-term potentiation (LTP). Thus, development of a specific CDKL5 inhibitor must be careful to exclude cross-talk with GSK3β activity. We synthesized and characterized specific, high-affinity inhibitors of CDKL5 that do not have detectable activity for GSK3β. These compounds are very soluble in water but blood-brain barrier penetration is low. In rat hippocampal brain slices, acute inhibition of CDKL5 selectively reduces postsynaptic function of AMPA-type glutamate receptors in a dose-dependent manner. Acute inhibition of CDKL5 reduces hippocampal LTP. These studies provide new tools and insights into the role of CDKL5 as a newly appreciated key kinase necessary for synaptic plasticity. Comparisons to rodent knock-out studies suggest that compensatory changes have limited the understanding of the roles of CDKL5 in synaptic physiology, plasticity, and human neuropathology

Progress towards a public chemogenomic set for protein kinases and a call for contributions

Protein kinases are highly tractable targets for drug discovery. However, the biological function and therapeutic potential of the majority of the 500+ human protein kinases remains unknown. We have developed physical and virtual collections of small molecule inhibitors, which we call chemogenomic sets, that are designed to inhibit the catalytic function of almost half the human protein kinases. In this manuscript we share our progress towards generation of a comprehensive kinase chemogenomic set (KCGS), release kinome profiling data of a large inhibitor set (Published Kinase Inhibitor Set 2 (PKIS2)), and outline a process through which the community can openly collaborate to create a KCGS that probes the full complement of human protein kinases

Strategy for Lead Identification for Understudied Kinases

In our manuscript we outline an approach in which we convert a promiscuous pyrimidine scaffold into narrowly selective, cell-active chemical leads for several understudied kinases, including DRAK1, BMP2K, and MARK4. These chemical tools will allow illumination of the function(s) of these poorly characterized kinases for the first time. Several of the understudied kinases that we inhibit with our pyrimidine-based compounds are also implicated in neurodegenerative disease, pushing the utility of kinase inhibitors outside of the oncology space and offering opportunities for the validation of therapeutic hypotheses attributed to these kinases.</p

Pretargeted radioimmunotherapy using genetically engineered antibody-streptavidin fusion proteins for treatment of non-hodgkin lymphoma.

Purpose: Pretargeted radioimmunotherapy (PRIT) using streptavidin (SAv)-biotin technology can deliver higher therapeutic doses of radioactivity to tumors than conventional RIT. However, "endogenous" biotin can interfere with the effectiveness of this approach by blocking binding of radiolabeled biotin to SAv. We engineered a series of SAv FPs that downmodulate the affinity of SAv for biotin, while retaining high avidity for divalent DOTA-bis-biotin to circumvent this problem.Experimental Design: The single-chain variable region gene of the murine 1F5 anti-CD20 antibody was fused to the wild-type (WT) SAv gene and to mutant SAv genes, Y43A-SAv and S45A-SAv. FPs were expressed, purified, and compared in studies using athymic mice bearing Ramos lymphoma xenografts.Results: Biodistribution studies showed delivery of more radioactivity to tumors of mice pretargeted with mutant SAv FPs followed by (111)In-DOTA-bis-biotin [6.2 +/- 1.7% of the injected dose per gram (%ID/gm) of tumor 24 hours after Y43A-SAv FP and 5.6 +/- 2.2%ID/g with S45A-SAv FP] than in mice on normal diets pretargeted with WT-SAv FP (2.5 +/- 1.6%ID/g; P = 0.01). These superior biodistributions translated into superior antitumor efficacy in mice treated with mutant FPs and (90)Y-DOTA-bis-biotin [tumor volumes after 11 days: 237 +/- 66 mm(3) with Y43A-SAv, 543 +/- 320 mm(3) with S45A-SAv, 1129 +/- 322 mm(3) with WT-SAv, and 1435 +/- 212 mm(3) with control FP (P &lt; 0.0001)].Conclusions: Genetically engineered mutant-SAv FPs and bis-biotin reagents provide an attractive alternative to current SAv-biotin PRIT methods in settings where endogenous biotin levels are high. Clin Cancer Res; 17(23); 7373-82. (C)2011 AACR

Conventional and Pretargeted Radioimmunotherapy with Bismuth-213 to Target and Treat CD20-Expressing Non-Hodgkin Lymphoma: A Preclinical Model for Consolidation Therapy to Eradicate Minimal Residual Disease.

Abstract 2705 Poster Board II-681 Conventional radioimmunotherapy (RIT) with directly radiolabeled anti-B cell antibodies (Ab) induces remissions in 50 to 80% of patients with relapsed or refractory indolent non-Hodgkin lymphomas (NHL). Although administering RIT as consolidation after chemotherapy improves response rates and produces long-term durable remissions in treatment-naive patients, the β-emitting radionuclides used in current RIT schemes may not be ideal for irradiating the microscopic tumors and the isolated tumor cells present in the setting of minimal residual disease (MRD). RIT with α-emitting radionuclides may be advantageous in the treatment of MRD because the short path length and high energies of α-particles produce optimal cytotoxicity at small target sites while minimizing damage to the surrounding normal tissues. Our group has successfully demonstrated that pretargeted RIT (PRIT) using streptavidin (SA)-Ab and radiolabeled biotin allows rapid specific localization of radioactivity at tumor sites. PRIT using α-emitting radionuclides may be particularly attractive since the most promising α-emitting radionuclides in clinical settings, such as 213 Bi (t½ = 46 min), have short half-lives and pretargeting allows the delivery of radioactivity to tumor sites before the activity decays. We therefore performed in vivo studies to evaluate the biodistribution of 213 Bi with PRIT. Athymic mice with B-cell NHL (Ramos) xenografts received a tetravalent anti-CD20 (1F5) single-chain (scFv) 4 SA fusion protein (FP) or a CC49 (scFv) 4 SA FP (non-binding negative control) followed by an N-acetyl galactosamine clearing agent (CA) and subsequent 213 Bi-DOTA-biotin infusion. Tumors, blood, and major organs were collected to determine the percent injected dose per gram (%ID/g) at various time points within ∼3 half-lives of 213 Bi. Maximal tumor uptake for 1F5 (scFv) 4 SA FP was 16.5 ± 7.0 %ID/g at 90 minutes vs. 2.3 ± 0.9 %ID/g for the control FP (p = 0.0001). Biodistributions of 213 Bi using a conventional RIT scheme with directly labeled Ab were also evaluated. Athymic mice with Ramos xenografts received 213 Bi labeled 1F5 Ab or 213 Bi labeled HB8181 Ab (a murine isotype matched nonbinding control). Maximum tumor uptake for 1F5 Ab was 3.0 ± 0.9 %ID/g at 180 minutes vs. 2.3 ± 0.7 %ID/g for the control Ab (p = 0.171). There were no significant differences in tumor uptake and normal organ distribution between the two Ab within 180 minutes of radiolabeled Ab injection presumably due to the protracted circulating half-life of radiolabeled Abs. These results were concordant with our previous experiments using other radionuclides, showing that maximal targeting of radiolabeled Ab occurs between 20 to 24 hours; well beyond the effective half-life of 213 Bi. When the results of PRIT and RIT studies were directly compared, tumor-to-blood ratios were 58 to 426-fold higher with PRIT than with conventional RIT. Tumor-to-normal organ ratios of nearly 100:1 were observed with PRIT compared to 3:1 or less with conventional RIT. Using the most favorable PRIT schemes defined in the biodistribution experiments, the therapeutic efficacy of 213 Bi was evaluated. Mice treated with PRIT using 1F5 (scFv) 4 SA FP followed by a CA and 600 μCi 213 Bi-DOTA-biotin experienced significant delays in tumor growth. The 1F5 (scFv) 4 SA FP treated animals had a mean tumor volume of 0.01 ± 0.02 vs. 203.38 ± 83.03 mm 3 for the CC49 control group at 19 days (p = 0.0006). The median survival for 1F5 group was not reached after 90 days; whereas, the median survival was 23 days for the CC49 group (p = 0.0019) and 16 days for untreated mice (p = 0.0023). The treatment was well tolerated, with no treatment-related mortalities in any group. These data demonstrate that PRIT using 213 Bi has a favorable biodistribution profile and excellent therapeutic efficacy. This model may be particularly effective in MRD settings and further studies are ongoing. Disclosures: No relevant conflicts of interest to declare