Development of a lyophilization formulation that preserves the biological activity of the platelet-inducing cytokine interleukin-11 at low concentrations

Recombinant human interleukin-11 (rhIL-11) is a licensed biological therape utic product in at least one country and is used to combat thrombocytopenia during chemotherapeutic regimens, as well as undergoing clinical trials fo r a range of other disorders. Following attempts to lyophilize IL-11 at low concentrations, it was clear that a significant loss of recoverable biolog ical activity occurred. Investigation of a variety of factors, including the type of container in w hich the rhIL-11 was lyophilized, revealed that surface adsorption to glass was a major factor resulting in loss of activity of rhIL-11 in solution (> 40% reduction after 3 h at room temperature), in addition to losses of acti vity post-lyophilization. To overcome this problem, different formulations containing combinations of human serum albumin (HSA), trehalose and Tween-2 0 have been investigated. Two formulations were successful ire entirely preserving the biological act ivity of rhIL-11 through lyophilization and subsequent reconstitution (pote ncy estimates of formulated relative to original material being greater tha n or equal to 0.97). Accelerated degradation studies, performed at interval s over a six-month period, demonstrated the stability of freeze-dried rhIL- 11 using these formulations (predicted annual reduction in potency after st orage at -20 degrees C less than or equal to 1.4%). In conclusion, we have developed a working combination of excipients (0.5% HSA, 0.1% trehalose and 0.02% Tween-20 in potassium phosphate buffer (pH 7. 4)) to formulate a stable rhIL-11 freeze-dried product in glass containers, with no lass in potency. These findings should facilitate development of l ow dose rhIL-11 products and be an indicator of caution to those using this and other material with similar physical properties, without taking approp riate precautions to avoid losses through adsorption.