The IL-2 Receptor (IL-2R) α subunit has low affinity for its ligand but has the ability (when bound to the β and ϒ subunit) to increase the IL-2R affinity 100-fold. Heterodimerization of the β and ϒ subunits of IL-2R is essential for signalling in T cells.
Commercial activity to bring an IL-2 drug to market was intense in the 1980s and '90s. By 1983, Cetus Corporation had created a proprietary recombinant version of IL-2 (Aldesleukin, later branded as Proleukin), with the alanine removed from its N-terminal and residue 125 replaced with serine.:76–77:201Amgen later entered the field with its own proprietary, mutated, recombinant protein and Cetus and Amgen were soon competing scientifically and in the courts; Cetus won the legal battles and forced Amgen out of the field.:151 By 1990 Cetus had gotten aldesleukin approved in nine European countries but in that year, the U.S. Food and Drug Administration (FDA) refused to approve Cetus' application to market IL-2. The failure led to the collapse of Cetus, and in 1991 the company was sold to Chiron Corporation. Chiron continued the development of IL-2, which was finally approved by the FDA as Proleukin for metastatic renal carcinoma in 1992.
By 1993 aldesleukin was the only approved version of IL-2, but Roche was also developing a proprietary, modified, recombinant IL-2 called teceleukin, with a methionine added at is N-terminal, and Glaxo was developing a version called bioleukin, with a methionine added at is N-terminal and residue 125 replaced with alanine. Dozens of clinical trials had been conducted of recombinant or purified IL-2, alone, in combination with other drugs, or using cell therapies, in which cells were taken from patients, activated with IL-2, then reinfused.Novartis acquired Chiron in 2006 and sold the aldesleukin business to Prometheus Laboratories in 2010.
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^Shi VY, Tran K, Patel F, Leventhal J, Konia T, Fung MA, Wilken R, Garcia MS, Fitzmaurice SD, Joo J, Monjazeb AM, Burrall BA, King B, Martinez S, Christensen SD, Maverakis E. 100% Complete response rate in patients with cutaneous metastatic melanoma treated with intralesional interleukin (IL)-2, imiquimod, and topical retinoid combination therapy: results of a case series. Journal of the American Academy of Dermatology. October 2015, 73 (4): 645–54. PMID 26259990. doi:10.1016/j.jaad.2015.06.060.