(T0930-08-49) Solving PK Challenges- Inhaled Peptide-Drug Conjugates Allow for Tunable PK Profiles, Maximizing Efficacy Whilst Reducing Dose and Dosing Frequency

Purpose: One key challenge that drug developers face is how to increase the plasma half-life of highly efficacious drugs¹. The desire to improve plasma half-life is two-fold, longer half-live equates to less frequent dosing for patients, and an improvement in side-effect profiles. The lung is an ideal controlled delivery route due to its convenience to the patient and drug absorption features². Herein we present a differentiated approach to solving this key drug development challenge, an inhaled peptide-drug conjugate, specifically a GLP-1 RA agonist, where we demonstrate that through controlled release of the GLP-1 RA agonist we achieve a spectrum of PK profiles, almost all of which confer efficacy in animal models of an otherwise “failed” drug candidate.

Methods: A series of 8 peptide-drug conjugates (PT-5001-5008) consisting of an 11-amino acid GLP-1 receptor agonist (PT-5000, an analog of compound 110 described in Haque et al 2010 conjugated to our proprietary SystemoPulseä lung-surfactant peptide) were made and tested^{3, 4}. PT-5001 incorporated a stable linker, whereas PT-5002-5008 were linked via a set of protease-cleavable linkers. Each of the cleavable linkers contained a specific sequence design for precise cleavage by lung-resident proteases to release free PT-5000 with its N-terminal Histidine intact. The 8 conjugates and free drug were administered intratracheally in a pharmacokinetic study in mice and plasma levels of free PT-5000 were measured at 0, 1, 2, 4, 8 and 24 hours. In a separate study, the 8 conjugates, free drug and semaglutide were tested in a Diet Induced Obesity (DIO) model in male C57BL/6J mice fed a standard high-fat diet (D12492). In this model, semaglutide was administered s.c. QD at a dose of 0.016 mg/kg; free drug PT-5000 was administered i.t. QD at a dose of 20 ug/mouse; and conjugates PT-5001-5008 were administered i.t. QOD at a dose of 20 ug/mouse (approximately 0.2 equivalents of PT-5000). The animals, 10 mice/group, were monitored periodically for body mass and feed intake over the course of 28 days post-dosing. Additional measures taken at the end of treatment prior to termination included fed glucose levels, DEXA scan on day 27; oral glucose tolerance test on day 30; and serum samples were collected for biochemistry and lipid profile on termination.

Results: The precisely engineered cleavage sites in the conjugates provided a spectrum of rates of controlled release of the GLP-1 RA as described by Cmax and Cmin@8hr (Figure 1). Free drug PT-5000 showed typical bolus kinetics, with Cmax of 22 ng/mL, exponential decay and Cmin@8hr unmeasurable (estimated plasma t-1/2 1 hour). Conjugate PT-5001 (designed to not release free drug), PT-5003 and PT-5007 showed no plasma levels of free drug over the course of 24 hours. In contrast, conjugates PT-5002, 5004, 5005, 5006 and 5008 achieved measurable plasma levels of free drug to at least 8 hours. Of these, PT-5002, PT-5004 and PT-5005 had the highest Cmax; 10, 9 and 8 ng/mL, respectively. Highest Cmin@8hr was observed for PT-5005 (8.5 ng/mL), approximately the same as its Cmax at 2 hours. PT-5002 and PT-5006 each exhibited Cmin@8hr of 3 ng/mL. Similar to PT-5005, PK for PT-5004 exhibited Cmin@8hr (3 ng/mL) nearly matching its Cmax at 2 hours (5.5 ng/mL). In the DIO model, all 5 conjugates exhibiting Cmin@8hr of 3 ng/mL or higher exhibited statistically significant reductions in body mass: PT-5002 (-12%), 5005 (-13%), 5006 (-8%) and 5008 (-11%) (Figure 2). By comparison, semaglutide achieved body mass reduction of -16%. In addition to the observed body mass reductions, the effective GLP-1 RA conjugates also showed reductions in all measures affected by semaglutide with the notable exception of lean mass, which was reduced by semaglutide but not affected by the conjugates.

Conclusion: The peptide-drug conjugation approach leveraging a surfactant peptide backbone linked by precise protease-sensitive cleavage sequences described herein represents a highly differentiated method to achieving tunable pharmacokinetic profiles. Administration of GLP-1 RA peptide-drug conjugates via inhalation resulted in therapeutically effective treatment of obesity in mice which was driven by low, steady plasma exposures. This controlled-release drug delivery method effectively "resurrected" this small, 11-amino-acid GLP-1 RA compound, achieving therapeutically relevant outcomes where the free drug did not. The SystemoPulse ätechnology, which includes precise cleavage sites for lung-resident proteases, is amenable to conjugation with a wide range of drugs including small molecules, peptides, protein and nucleotide drugs. In conclusion, the platform can reduce dosing frequency for compounds with short half-life, thus improving the success of a drug candidate, and by matching the enzymatic release rate with drug clearance rate, this platform can achieve the lowest required effective exposure, which reduces the bolus effect and potential for unwanted systemic side effects.

References: 1. Smith, D. A., Beaumont, K., Maurer, T. S., & Di, L. (2018). Relevance of Half-Life in Drug Design. Journal of Medicinal Chemistry, 61(10), 4273–4282.
2. Labiris, N. R., & Dolovich, M. B. (2003). Pulmonary drug delivery. Part I: Physiological factors affecting therapeutic effectiveness of aerosolized medications. British Journal of Clinical Pharmacology, 56(6), 588–599.
3. Mapelli, C., Natarajan, S. I., Meyer, J.-P., Bastos, M. M., Bernatowicz, M. S., Lee, V. G., Pluscec, J., Riexinger, D. J., Sieber-McMaster, E. S., Constantine, K. L., Smith-Monroy, C. A., Golla, R., Ma, Z., Longhi, D. A., Shi, D., Xin, L., Taylor, J. R., Koplowitz, B., Chi, C. L., … Ewing, W. R. (2009). Eleven Amino Acid Glucagon-like Peptide-1 Receptor Agonists with Antidiabetic Activity. Journal of Medicinal Chemistry, 52(23), 7788–7799.
4. Haque, T. S., Lee, V. G., Riexinger, D., Lei, M., Malmstrom, S., Xin, L., Han, S., Mapelli, C., Cooper, C. B., Zhang, G., Ewing, W. R., & Krupinski, J. (2010). Identification of potent 11mer Glucagon-Like Peptide-1 Receptor agonist peptides with novel C-terminal amino acids: Homohomophenylalanine analogs. Peptides, 31(5), 950–955.

Figure 1: Concentration of GLP-1 RA in plasma over time highlights the precisely engineered cleavage sites in the conjugates that provide a spectrum of rates of controlled release of the GLP-1 RA as described by Cmax and Cmin@8hr.

Figure 2: In the DIO model, all 5 conjugates exhibiting Cmin@8hr of 3 ng/mL or higher exhibited significant reductions in percent body mass at the primary endpoint on Day 28 compared to baseline.