Recommendations of the Oligonucleotide Safety Working Group's Formulated Oligonucleotide Subcommittee for the Safety Assessment of Formulated Oligonucleotide-Based Therapeutics.

The use of lipid formulations has greatly improved the ability to effectively deliver oligonucleotides and has been instrumental in the rapid expansion of therapeutic development programs using oligonucleotide drugs. However, the development of such complex multicomponent therapeutics requires the implementation of unique, scientifically sound approaches to the nonclinical development of these drugs, based upon a hybrid of knowledge and experiences drawn from small molecule, protein, and oligonucleotide therapeutic drug development. The relative paucity of directly applicable regulatory guidance documents for oligonucleotide therapeutics in general has resulted in the generation of multiple white papers from oligonucleotide drug development experts and members of the Oligonucleotide Safety Working Group (OSWG). The members of the Formulated Oligonucleotide Subcommittee of the OSWG have utilized their collective experience working with a variety of formulations and their associated oligonucleotide payloads, as well as their insights into regulatory considerations and expectations, to generate a series of consensus recommendations for the pharmacokinetic characterization and nonclinical safety assessment of this unique class of therapeutics. It should be noted that the focus of Subcommittee discussions was on lipid nanoparticle and other types of particulate formulations of therapeutic oligonucleotides and not on conjugates or other types of modifications of oligonucleotide structure intended to facilitate delivery.

Characterization of a new in vivo hollow fiber model for the study of progression of prostate cancer to androgen independence.

Research investigating the molecular events underlying progression of prostate cancer to androgen independence has been impeded by the lack of an appropriate in vivo model that yields "pure" populations of prostate cancer cells that are not contaminated with host cells. Here we characterize a new in vivo model that uses hollow fibers and allows for the retrieval of uncontaminated prostate cancer cells during various stages of endocrine progression to androgen independence in male immunocompromised mice. Prostate-specific antigen (PSA) gene expression, proliferation of cells, and histology were examined in these mice before and after castration. LNCaP cells seeded at a density of 1 x 10(7) cells/ml, or a total of approximately 4.8 x 10(6) cells/animal, provided measurable serum PSA levels that increased in intact (noncastrated) animals, decreased by 80% to a nadir after castration, and subsequently increased by 4 weeks after castration, indicating progression to androgen independence. In vivo proliferation of LNCaP cells inside the fibers continued in the presence of androgens and continued to increase, albeit at a slower rate, in the castrated animals. Histology of cells cultivated in hollow fibers demonstrated that initially the cells grew along the wall of the fiber and tended to stack up, forming layers and scaffold structures resembling a solid tumor. Fibers removed from castrated animals with elevated levels of serum PSA contained spheroids of cells that had detached from the fiber wall. The development of the LNCaP hollow fiber model described here provides a reproducible means of obtaining "pure" populations of LNCaP cells during different stages of progression to androgen independence for molecular analysis requiring RNA and protein extracts free of host cell contamination.