XL-protein develops and commercializes its ground-breaking PASylation® technology, which enables the design of biopharmaceuticals with extended plasma half-life and enhanced action. Based on a strong proprietary technology platform, XL-protein is engaged in a growing number of partnerships with international pharmaceutical and biotech companies at various levels. ‘PASylation’ involves the genetic fusion or chemical conjugation of a therapeutic protein or pharmaceutically active compound with a conformationally disordered polypeptide of defined sequence comprising the small natural amino acids Pro, Ala, and/or Ser. Due to the biophysical size effect, the typically rapid clearance via renal filtration of the original drug can be retarded by a factor 10–100, depending on the length of the PAS chain. PAS sequences are highly soluble while lacking charges, they are biochemically inert, non-toxic and non-immunogenic, and they show high stability in blood plasma but are biodegradable by intracellular proteases.

The short circulation half-life of almost all genuine biopharmaceuticals — except for full size antibodies — poses a strong limitation for the development of efficacious biologics. Not only frequent dosing is a burden for patients, and the large amount of costly active pharmaceutical ingredient is a challenge for public healthcare, but also the quickly fading drug concentration in blood after injection prevents maximal response in organs and tissues. Previous technologies, like PEGylation, alleviate this problem only in part, or they come along with other caveats such as poor biodegradability and accumulation in the body. PASylation, which achieves dramatic half-life extension on the basis of a purely biologic polymer, paves the way to next generation biobetters with durable effect and enhanced action. Our mission is to serve both patient needs and pharmaceutical market requirements by turning promising laboratory candidates with proven mode of action into viable biopharmaceutical drug candidates with tailored pharmacokinetic and pharmacodynamic properties, thus enabling clinical translation.