The IPDC is one of three components of the molecular imaging aspect of the NIH Roadmap initiative, with the other two being high specificity/high sensitivity probes, and the set-up of an imaging probe database (MICAD). The IPDC will produce known imaging probes for the research community in cases where there is no viable commercial supplier, as well as to generate novel imaging probes for preclinical biomedical research. The new IPDC laboratories are under construction at 9800 Medical Center Drive in Rockville, MD, and are expected to be completed in October 2006.? ? On March 1 the first solicitation for IPDC projects was sent from Dr. Gottesman?s office to principal investigators (PIs) within NIH. Nineteen PIs contacted IPDC with a possible view to having work performed. The Director of the IPDC discussed most projects individually with each PI, advised on synthetic approaches and IPDC steering committee submission strategies, and projects that were deemed sufficiently well developed were considered by the steering committee. The 19 PIs were Dr. Balaban (NHLBI), Dr. Baron (NAIAD), Dr. Braun (NIDCD), Dr. Cherukuri (NCI), Dr. Choyke (NCI), Dr. Fung (CC), Dr. Gandhirbahce (NICHD), Dr. Gorospe (NIA), Dr. Hawkins (NCI), Dr. Iadarola (NIDCR), Dr. Isaac (NINDS), Dr. Jacobson (NIDDK), Dr. Kim (NEI), Dr. Knutson (NHLBI), Dr. Le Grice (NCI), Dr. Levine (NHLBI), Dr. Star (NIDDK), Dr. Ungerleider (NIMH), Dr. Young (NIMH). IPDC currently occupies a small temporary space in building 50, and has five staff members (3 PhD, 1 BS) on board.? ? Bench work has been performed on the following projects:? ? 1) Preparation of a colorless Coomassie dye analog to enable the probing of proteins without imparting upon them the compromising deep blue color of the original dye (for Dr. Balaban at NHLBI; non-literature method). Two dye analogs were made and given to Dr. Balban?s laboratory for further testing. A patent application was prepared and submitted to the USPTO to cover the technology. Repeat quantities are being supplied as needed.? ? 2) Preparation of a fluorescent trifunctional linker (NBzM) for use in the probing of protein-protein interactions in HIV and cancer (for Dr. Le Grice and several other investigators at NCI; literature method, Bioconjugate Chem., 15:969-982,2004, seven synthetic steps). Fifty milligrams sent to NCI, Frederick (only microgram amounts are needed for each experiment), with thirty milligrams retained for stability & other in-house IPDC testing, and to fulfill other requests.? ? 3) Preparation of three highly fluorescent pteridine-based probes as nucleoside analogs of guanosine and adenosine for incorporation into oligonucleotides, resulting in the ability to place a probe directly into an oligonucleotide backbone (for Mary Hawkins at NCI; literature methods, Anal. Biochem., 298:231-240, 2001, and Nucleosides & Nucleotides, 17:175-186, 1998, The first of the three probes, 6MAP [~ 50 mg], was made in a seven-step synthesis, with IPDC yield improvements). Larger amounts of material (5 gram scale) were made later and are now available. The 6-MAP agent has been activated for incorporation into standard automated oligonucleotide syntheses. The synthesis of the second probe, 3-MI, is now almost complete with around a dozen synthetic steps of the approximately 15 total now done. This probe is also being produced on the larger, 5 gram, scale. Work will begin later in the year on the final probe (6-MI).? ? 4) Preparation of the probe biocytin-DOTA-gadolinium for use as a new magnetic resonance-visible neural tracer for functional imaging studies in order to map connections between different brain regions (for Dr. Ungerleider at NIMH, non-literature method). A product is awaiting final structure validation, and has been made at the ~ 100 milligram level. Dr. Ungerleider has also requested two other probes from IPDC, an iron oxide MION and a gadolinium complex of horseradish peroxidase-wheat germ agglutinin.? ? 5) Preparation of six variant probes based on gadolinium-labeled PAMAM G2, PAMAM G4 and PAMAM G6 dendrimers. (For Dr. Choyke at NCI and for multiple collaborating investigators at NCI, NINDS and NIDDK; literature methods with modifications, J. Chromatog. A.,771:63-69, 1997, and Mag. Res. Med., 46:1169-1173, 2001, and references cited therein, 7-8-step syntheses ending in substitution onto dendrimers). Gram quantities of the activated derivative from the 7-step synthesis were made, and are available for dendrimer conjugate synthesis. Samples of each of the first six Gd-DTPA-dendrimer conjugates have been made and tested analytically, and await final validation/approval by the requesting laboratory. Going forward, the project also presents a significant challenge in ensuring batch-to-batch reproducibility via adequate quality control testing, as continuing lots are produced with scale-up.? ? 6) Starting materials have been obtained for the synthesis of 5-carboxyflash-EDT2 succinimidyl ester to be used as part of a protease-resistant probe for tracking prion infection of cells (for Dr. Baron at NIAID, literature methods, JACS, 124:6063-6076, 2002 and Bioconjugate Chem., 8:495-497, 1997, and references cited therein, six synthetic steps). Dr. Baron has also requested a second probe involving a 14-step synthetic sequence.? ? Other: Preparation of the probe precursor CTMIO for use as a nitroxide MRI contrast agent (for Drs. Mitchell and Krishna at NCI, literature method, JCS Perkin Trans., 2:1285-1291, 2000, and Aust. J. Chem., 36:397-401, 1983, four synthetic steps) is slated to begin with the arrival of the next staff hire.? ? IPDC work on probes suggested by Drs. Braun, Gandhirbahce, and Jacobson are pending receipt of required intermediates and/or information to be supplied to IPDC by collaborators (two of these probes may possibly be further delayed, for another reason: until we have our own radiochemistry laboratory set up in October.? ? A series of other projects are planned once more staff comes aboard and the new facility opens in the next two months.? ? Discussions are in progress with scientists at the MICAD imaging database aspect of the Roadmap (ML-5), with a view to depositing all probe information, including synthetic details, into that database at the appropriate times, with PI approvals.
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