Method for purification of IL-12

A method for purification of IL-12 heterodimer comprising the following steps in the following order:

• (a) loading a solution containing IL-12 heterodimer onto an anion exchange resin at a pH of 8.0, washing the loaded anion exchange resin with a solution of a pH of 5.5, and eluting said IL-12 heterodimer from said anion exchange resin;
• (b) loading the eluate of step (a) onto a cation exchange resin at a pH of 6.0, washing the loaded cation exchange resin with a solution of a pH of 7.2, and eluting said IL-12 heterodimer from said cation exchange resin;
• (c) loading the eluate of step (b) onto a hydrophobic interaction chromatography (HIC) resin, washing the loaded HIC resin with a solution comprising isopropanol at a concentration sufficient to elude excess p40 subunit of the heterodimer (p40) from said loaded HIC resin without eluting said IL-12 heterodimer, and eluting said IL-12 heterodimer from said HIC resin;
• (d) concentrating the eluate of step (c) by tangential-flow ultrafiltration, and
• (e) loading the concentrate from step (d) onto a size exclusion resin and eluting said IL-12 heterodimer from said size exclusion resin.