Intact bioactivities and improved pharmacokinetic of the SL335-IFN-β-1a fusion protein that created by genetic fusion of SL335, a human anti-serum albumin fab, and human interferon-β.

Recombinant human interferon beta (rIFN-β) has long been used as a first-line treatment for multiple sclerosis (MS), and any attempt to develop a long-acting rIFN-β is desirable since only one pegylated version of long-acting rIFN-β-1a (Plegridy) is currently available in clinics. Previously, we reported that SL335, a human Fab molecule specific to serum albumin, exhibits an extended serum half-life via utilizing the FcRn recycling mechanism. With the ultimate goal of developing a long-acting rIFN-®, we generated a fusion construct by linking human IFN-β cDNA to the C-terminus of the SL335 H chain at the DNA level followed by expression of the fusion protein, referred to as SL335-IFN-β-1a, in Chinese hamster ovary-S (CHO-S) cells. In its N-linked glycosylated form, the resulting fusion protein was easily purified from the culture supernatant via a three-step chromatography process. In vitro functional assays revealed that the fusion protein retained its intrinsic binding capabilities to human serum albumin (HSA) and interferon α/β receptor (IFNAR) that were almost identical to those of parental SL335 and rIFN-β-1a (Rebif). In addition, the fusion protein possessed an antiviral potency and anti-proliferation activity comparable to those of Rebif. In pharmacokinetic (PK) analyses using Lewis rats and cynomolgus monkeys, SL335-IFN-β-1a exhibited at least a two-fold longer serum half-life and a significantly reduced renal clearance rate compared to those of Rebif. Finally, a four-week repeated dose toxicity study revealed no abnormal toxicological signs. In conclusion, our results clearly demonstrated that SL335-IFN-β-1a is worthy of further development as an alternative long-acting IFN-β therapeutic.