Orphan chemicals

While the responses to the voluntary HPV program were substantial, there were nevertheless chemicals that no one sponsored, and those chemicals are often referred to as orphan chemicals. As of EPA s most recent update on its Web site, from 2006, 267 chemicals fell into this category. Data 

http //www.epa.gov/chemrtk/pubs/general/basicinfo.htm. The HPV Challenge Program had twenty-eight hundred chemicals on its list at one time. 71 Fed. Reg. 13708, 13709 (Mar. 16, 2006). 

http //www.epa.gOv/oppt/existingchemicals/pubs/enhanchems.html newreg. 

The list of orphan chemicals is revised periodically and is available at http //www.epa.gov/ hpv/pubs/general/hpvunspn.pdf. 

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R. Dennison, Orphan Chemicals in the HPV Challenge A Status Report, Environmental Defense, Washington, DC, June 2004. 

On July 24,2008, EPA issued a proposed test rule for the second group of 19 HPV chemical substances. The proposed rule has basically the same substance as the first test rule on HPV chemical substances. It also requests additional testing on several SIDS endpoints for five chemicals in the first HPV test rule because EPA, after evaluation, determined the existing data and experience were not sufficient to predict the effect of those substances on health or the environment. EPA has said that the issuance of a test rule on a substance does not preclude it from requiring additional testing, if a need for such testing becomes clear. EPA expects to finalize the second test rule in 2010 and propose subsequent test rules for additional orphan chemicals. ... 

Orphan chemicals list for the HPV Challenge Program is revised... 

Tang Herbal, 147 Target-based drug discovery biological targets, 180-184 chemical end point in, 180 chemical tools, 178-179 definition of, 5 description of, 175-177 linear approach, 176 orphan receptors, 180 preclinical process in, 176-177 random variation in gene expression, 178... 

Synthetic molecule or peptide that is able to activate an orphan receptor but differs in chemical structure from the natural endogenous ligand... 

Ligands of the RXR-heterodimer group and the orphan receptors are chemically more diverse than the ligands of the steroid family. Representative hgands of this group are the retinoids all-trans retinoic acid, 9-cis retinoic acid, the T3 hormone and vitamin D3 (fig. 4.1). 

Other organoarsenicals, most notably lewisite (dichloro[2-chlorovinyl]arsine), were developed in the early twentieth century as chemical warfare agents. Arsenic trioxide was reintroduced into the United States Pharmacopeia in 2000 as an orphan drug for the treatment of relapsed acute promyelocytic leukemia and is finding expanded use in experimental cancer treatment protocols (see Chapter 54). Melarsoprol, another trivalent arsenical, is used in the treatment of advanced African trypanosomiasis (see Chapter 52). 

Willson, T. (2003). Chemical genomics of orphan nuclear receptors. Ernst Schering Research Foundation Workshop, 29-42. 

Dapporto, L., Sledge, F. W. and Turillazzi, S. (2005). Dynamics of cuticular chemical profiles of Polistes dominulus workers in orphaned nests (Hymenoptera, Vespidae). 

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