Immunomedics Reports Progress With Labeling Proteins, Including Antibodies, For Improved PET Imaging

VANCOUVER, British Columbia, June 12, 2013 (GLOBE NEWSWIRE) -- Immunomedics, Inc. (Nasdaq:IMMU), a biopharmaceutical company primarily focused on the development of monoclonal antibody-based products for the targeted treatment of cancer, autoimmune and other serious diseases, today reported progress with labeling temperature-sensitive molecules using fluorine-18 ( 18F) for improved positron-emission tomography (PET) imaging of diseases. Results of this study were presented by William McBride, Ph.D., Senior Director, Peptide Chemistry.

The Company previously published a novel method of radiolabeling peptides with 18F known as AlF. 1 Eleven publications have since tracked the development of this patented method, including a recently published review. 2 The Company simplified the approach with the development of a lyophilized kit that permits the radiolabeling of peptides within about 20 minutes, with yields exceeding 70% and high specific activity. 3 A similar radiolabeling kit utilizing the AlF technology was recently validated clinically by National Institute of Health scientists, in collaboration with Chinese physicians, who successfully imaged all sites of tumor in 9 lung cancer patients with a 18F-labeled peptide. 4 More importantly, as recently reported by us ( ), this method is now protected by 11 U.S. issued patents.

18F labeling by the AlF procedure requires the use of metal-binding ligands, such as NODA or NOTA, which capture a highly stable aluminum- 18F complex. The Company previously reported the creation of the NODA-MPAA ligand for highly efficient direct radiolabeling of peptides and other compounds that can withstand high temperatures, and introduced a 2-step procedure that could be used for radiolabeling heat-sensitive compounds, such as antibody fragments. (For more information, please visit the Company's press release at ).

The current study presented at this year's SNMMI Annual Meeting was aimed at creating new NODA-based ligands for improved radiofluorination yields at lower temperatures. Two new ligands, a pyridine-NODA and a triazole-NODA, were synthesized and shown to have higher labeling yields than NODA-MPAA, especially at lower temperatures. Furthermore, no co-solvent was needed for the peptide linked with triazole-NODA ligand. Both of the F-18-labeled peptides were stable in human serum at 37 oC for at least 4 hours.

In a second oral presentation at this year's SNMMI Annual Meeting, Shankar Vallabhajosula, Ph.D., Nuclear Medicine/Molecular Imaging, Weill Cornell Medical College, New York, NY, reported progress toward the commercial development of radiopharmacy manufacturing to prepare multi-dose 18F labeled peptides and proteins using the Company's patented AlF-labeling method. Their new study evaluated processes aimed at optimizing the radiolabeling procedure for multi-dose preparation of IMP485, a hapten-peptide used for pretargeting, a highly sensitive and specific method for targeting cancers using a bispecific antibody. 5

The optimized procedure had 60% yields, with specific activity high at 5.1 Ci (137.8 GBq)/μmole. Sep-Pak purification resulted in >90% radiochemical purity (RCP) and HPLC purification was not required. The investigators further found that a widely used and simple procedure known as instant thin-layer chromatography (ITLC) using silicon gel and water was suitable for the assessment of RCP. Using these procedures, 18F-IMP-485 may be an ideal radiopharmaceutical for ImmunoPET studies based on the pretargeting approach pioneered by the Company.

This study was supported in part by Award Number R44RR028018 from the National Center for Research Resources and the National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health.

If you liked this article you might like

Kite Takeover by Gilead Lifts Biotech Stocks

Biotech Movers: Immunomedics, Aerie, Exelixis

Immunomedics, Seattle Genetics Scrap License Deal

Biotech Movers: Immunomedics Shares Jump After License Pact with Seattle Genetics Is Terminated

Bullish and Bearish Reversals for This Week