Prolonged, Controllable Protein Production of cDNA-Encoded hGH Maintained at Therapeutic Serum Levels Following One Systemic Administration of a Non-Viral, Non-Integrating, DNA-and Liposome-Based in vivo Gene Therapy Platform in Immunocompetent Mice

Abstract

Abstract Recombinant human growth hormone (rhGH), the mainstay of hGH replacement therapy, is injected daily for years to enable children to achieve normal stature. Daily rhGH injections are required because its serum-T1/2 is <20 minutes. Human trials testing T1/2-extending rhGH proteins are promising, but even weekly rhGH administration poses potential short and long-term toxicity risks, including exacerbation of diabetes or hypertension and potential for oncogenesis. Frequent hGH injections produce non-physiologic IGF-I profiles, (peak serum IGF-I frequently supra-normal, trough IGF-I concentrations at baseline). Therefore, a safe, effective, single administration hGH approach that maintains hGH and IGF-I serum concentrations within their respective therapeutic ranges for approximately one year could offer significant advantages. Accordingly, DNARx tested HEDGESTM, it’s non-viral, non-integrating, DNA-and liposome-based systemic, in vivo gene therapy approach to produce long-term hGH serum levels within the therapeutic range (1 -10 ng/ml) in immunocompetent mice. Previously, one systemic HEDGES-human granulocyte colony stimulating factor (hG-CSF, serum T1/2<3 hours) cDNA administration produced durable therapeutic hG-CSF serum levels (Science advances, 2019, 5, 2019). Importantly, simply by modifying selected aspects of HEDGES’s DNA vector and liposomal components, the duration of serum hG-CSF protein production was controllable over a broad temporal range. Long-term assessment of serum hGH in immunocompetent mice was assessed by injecting either one HEDGES administration or one administration followed by one re-dose of DNA vectors expressing either A) wildtype hGH cDNA (HEDGES-1) or B) wildtype hGH fused to selected serum protein T1/2-extending DNA sequences (HEDGES-2), with these results: 1) One HEDGES-1 administration produced slowly-increasing, but sub-therapeutic hGH serum levels from day 7 to day 99 after injection. From day 99 on, serum hGH levels remained within the therapeutic range for > 230 days; 2) Concurrently, hGH-induced elevation of endogenous mouse serum IGF-I levels remained between 1 to 3 fold above baseline. 3) One HEDGES-1 re-injection was administered 35 days after initial injection, a time when hGH serum levels remained sub-therapeutic. By day 7, one re-injection further elevated cDNA-encoded hGH serum levels into the therapeutic range, maintaining them for >175 days; 4) One HEDGES-2 administration produced therapeutic hGH serum levels by day 7 that were maintained for >250 days. These studies demonstrate the feasibility of achieving very long-term therapeutic levels of hGH and IGF-I following 1-2 injections. DNARx is now focused on selectively modifying its HEDGES hGH cDNA vectors and liposomal components to produce hGH serum levels within the therapeutic range for the equivalent of one human year following administration