Immunogenicity and toxicokinetics assessment of the mono-PEGylated recombinant human interleukin-11 in cynomolgus monkeys.

AIM: Protein therapeutics have potential to elicit immune responses resulting in undesirable anti-drug antibodies (ADA) that might affect product efficacy and patient safety, and should be assessed in animals before applying the treatment to humans. In this paper, we aim to assess the immunogenicity and toxicokinetics of the mono-PEGylated recombinant human interleukin-11 (rhIL-11), a novel protein therapeutic for the treatment of chemotherapy-induced thrombocytopenia, in repeated administration to cynomolgus monkeys. MAIN METHODS: Enzyme-linked immunosorbent assay (ELISA) methods were developed to measure ADA responses and plasma PEGylated IL-11 (PEG-IL11) concentration in monkeys. Assay parameters of immunogenicity and toxicokinetics methods were evaluated during validation in accordance with regulatory guidelines. We also employed cell-based assays to test the neutralizing activity of ADA provoked in monkeys. KEY FINDINGS: The results showed that weak immunogenicity occurred in some monkeys after receiving repeated dose of 0.1-0.3 mg/kg by subcutaneous administration and disappeared after the recovery period. More pronounced immunogenicity occurred at high dose of 0.9 mg/kg, with a higher positive rate and titer, and some ADAs had neutralizing activity, but it can be greatly reduced after recovery. Such ADAs generated in monkeys may be accounted for the plasma toxicokinetics changes of PEG-IL11 and a minor reduction in systemic exposure. SIGNIFICANCE: These methods have been successfully applied to immunogenicity and toxicokinetic studies of PEG-IL11 in repeated dose toxicity following subcutaneous administration to monkeys, and could be successfully used in clinical trials after some modifications.

Pharmacokinetic and Pharmacodynamic Evaluation of Different PEGylated Human Interleukin-11 Preparations in Animal Models.

Treating thrombocytopenia induced by chemotherapy remains an unmet-medical need. The use of recombinant human interleukin-11 (rhIL-11) requires repeated injections and induces significant fluid retention in some patients. Modification of human interleukin-11 with chemically inert polyethylene glycol polymer (PEG) may extend the peripheral circulation half-life leading to an improved pharmacokinetic and pharmadynamic profile. In this study, a number of rhIL-11 PEG conjugates were created to determine the optimal approach to prolong circulating half-life with the most robust pharmacological effect. The lead candidate was found to be a single 40-kDa Y-shaped PEG linked to the N-terminus, which produced a long-lasting circulating half-life, enhanced efficacy and alleviated side effect of dilutional anemia in healthy rat models. This candidate was also shown to be effective in myelosuppressive rats in preventing the occurrence of severe thrombocytopenia while ameliorating dilutional anemia, compared to rats receiving daily administration of unmodified rhIL-11 at the same dose. These data indicated that a single injection of the selected modified rhIL-11 for each cycle of chemotherapy regimen is potentially feasible. This approach may also be useful in treating patients of acute radiation syndrome when frequent administration is not feasible in a widespread event of a major radiation exposure.

Preclinical evaluation of the mono-PEGylated recombinant human interleukin-11 in cynomolgus monkeys.

The mono-PEGylated recombinant human interleukin-11 (rhIL-11) was evaluated for its pharmacology and toxicology profile in non-human primates. This PEGylated IL-11 (PEG-IL11) showed a much prolonged circulating half-life of 67h in cynomolgus monkeys as compared to its un-PEGylated counterpart (~3h) through subcutaneous administration, implicating that a single injection of the recommended dose will effectively enhance thrombopoiesis in humans for a much longer period of time compared to rhIL-11 in humans (t1/2=6.9h). The toxicokinetics study of single dose and multiple doses showed that systemic exposure was positively correlated with the dosing level, implying that efficacy and toxicity were mechanism-based. A single high dose at 6.25mg/kg through subcutaneous route revealed tolerable and transient toxicity. Multiple-dose in monkeys receiving 0.3mg/kg weekly of the drug developed only mild to moderate toxicity. Major adverse events and immunogenicity in monkeys were only observed in the overdose groups. Bones were positively impacted; while reversible toxicities in heart, liver, kidney and lung observed were likely to be consequences of fluid retention. In summary, the PEG moiety on rhIL-11 did not elicit additional toxicities, and the drug under investigation was found to be well tolerated in monkeys after receiving a single effective dose of 0.1-0.3mg/kg through subcutaneous delivery, which may be allometrically scaled to a future clinical dose at 30-100µg/kg, creating a potential long acting, safer, and more convenient treatment approach based on rhIL-11.

Efficient expression and isolation of recombinant human interleukin-11 (rhIL-11) in Pichia pastoris.

Current source of recombinant human interleukin-11 (rhIL-11) is isolated from a fusion protein expressed by E. coli that requires additional enterokinase to remove linked protein, resulting in product heterogeneity of N-terminal sequence. Due to lack of glycosylation, rhIL-11 is suitable to be expressed by yeast cells. However, the only available yeast-derived rhIL-11 presents an obstacle in low production yield, as well as an unamiable process, such as the use of reverse-phase chromatography employing plenty of toxic organic solvents. Our findings showed that the low yield was due to self-aggregation of rhIL-11. A novel process recovering bioactive rhIL-11 from the yeast secretory medium therefore has been developed and demonstrated, involving fermentation from Pichia pastoris, followed by a two-phase extraction to precipitate rhIL-11. After renaturing, the protein of interest was purified by a two-column step, comprising a cation-exchanger, and a hydrophobic interaction chromatography in tandem at high sample loads that was facile and cost-effective in future scale-up. Identity and quality assessments confirmed the expected amino acid sequence without N-terminal heterogeneity, as well as high quality in potency and purity. Such a process provides an alternative and adequate supply of the starting material for the PEGylated rhIL-11.

Synthesis and characterization of a native, oligomeric form of recombinant severe acute respiratory syndrome coronavirus spike glycoprotein.

We have expressed and characterized the severe acute respiratory syndrome coronavirus (SARS-CoV) spike protein in cDNA-transfected mammalian cells. The full-length spike protein (S) was newly synthesized as an endoglycosidase H (endo H)-sensitive glycoprotein (gp170) that is further modified into an endo H-resistant glycoprotein (gp180) in the Golgi apparatus. No substantial proteolytic cleavage of S was observed, suggesting that S is not processed into head (S1) and stalk (S2) domains as observed for certain other coronaviruses. While the expressed full-length S glycoprotein was exclusively cell associated, a truncation of S by excluding the C-terminal transmembrane and cytoplasmic tail domains resulted in the expression of an endoplasmic reticulum-localized glycoprotein (gp160) as well as a Golgi-specific form (gp170) which was ultimately secreted into the cell culture medium. Chemical cross-linking, thermal denaturation, and size fractionation analyses suggested that the full-length S glycoprotein of SARS-CoV forms a higher order structure of approximately 500 kDa, which is consistent with it being an S homotrimer. The latter was also observed in purified virions. The intracellular form of the C-terminally truncated S protein (but not the secreted form) also forms trimers, but with much less efficiency than full-length S. Deglycosylation of the full-length homotrimer with peptide N-glycosidase-F under native conditions abolished recognition of the protein by virus-neutralizing antisera raised against purified virions, suggesting the importance of the carbohydrate in the correct folding of the S protein. These data should aid in the design of recombinant vaccine antigens to prevent the spread of this emerging pathogen.