MacKay Lab - Cognate Drug Receptors

Small molecule chemotherapeutics, although routinely used in the clinic, suffer from poor drug properties, including low water solubility, rapid plasma clearance, and non-specific bio-distribution causing toxic side effects. Our cognate drug receptor technology utilizes receptor-elastin like polypeptide (ELP) fusion proteins to facilitate delivery of drugs with sub-optimal physicochemical, toxicological, and pharmacokinetic properties.

For example, rapamycin, a clinically approved cytostatic and immunosuppressant is insoluble in water. Thus it requires non-aqueous solvents for delivery, displays sub-optimal pharmacokinetics in humans, partitions heavily into red blood cells, and causes severe stomatitis, hypercholesterolemia, and hypertriglyceridemia. To address these issues, we engineered FKBP-ELP fusion proteins to enable potent and safer delivery of rapamycin. FKBP, a cognate protein receptor of rapamycin solubilizes and stabilizes the drug. Since these fusion proteins are appropriately sized nanoparticles, they can also extend the plasma residence time by slowing renal filtration and promoting tumor accumulation, thereby reducing drug toxicity. Moreover, the delivery vehicle being proteinaceous in nature, is bio-degradable and bio-compatible.

Based on the promising efficacy of Rapamycin loaded FKBP-ELP fusion proteins, we have expanded our technology to facilitate delivery of other potent small molecules, which we are evaluating in models of cancer and autoimmune disorders.

Selected Publications

Berunda Polypeptides: Multi-Headed Fusion Proteins Promote Subcutaneous Administration of Rapamycin to Breast Cancer In Vivo
Jugal P. Dhandhukia, Zhe Li, Santosh Peddi, Shruti Kakan, Arjun Mehta, David Tyrpak, Jordan Despanie, J. Andrew MacKay
Theranostics 2017; 7(16):3856-3872.

Elastin-based protein polymer nanoparticles carrying drug at both corona and core suppress tumor growth in vivo
Pu Shi, Suhaas Aluri, Yi-An Lin, Mihir Shah, Maria Edman-Woolcott, Jugal Dhandhukia, Honggang Cui, J Andrew MacKay
J Control Release. 2013 Nov 10; 171(3): 330–338.

A rapamycin-binding protein polymer nanoparticle shows potent therapeutic activity in suppressing autoimmune dacryoadenitis in a mouse model of Sjögren’s syndrome
Mihir Shah,* Maria C. Edman,* Srikanth R. Janga, Pu Shi, Jugal Dhandhukia, Siyu Liu, Stan G. Louie, Kathleen Rodgers, J. Andrew MacKay, and Sarah F. Hamm-Alvarez
J Control Release. 2013 Nov 10; 171(3): 269–279.

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Berunda Polypeptides: Multi-Headed Fusion Proteins Promote Subcutaneous Administration of Rapamycin to Breast Cancer In Vivo

Jugal P. Dhandhukia, Zhe Li, Santosh Peddi, Shruti Kakan, Arjun Mehta, David Tyrpak, Jordan Despanie, J. Andrew MacKay

ABSTRACT Recombinant Elastin-Like Polypeptides (ELPs) serve as attractive scaffolds for nanoformulations because they can be charge-neutral, water soluble, high molecular weight, monodisperse, biodegradable, and decorated with functional proteins. We recently reported that fusion of the FK-506 binding protein 12 (FKBP) to an ELP nanoparticle (FSI) reduces rapamycin (Rapa) toxicity and enables intravenous (IV) therapy in both a xenograft breast cancer model and a murine autoimmune disease model. Rapa has poor solubility, which leads to variable oral bioavailability or drug precipitation following parenteral administration. While IV administration is routine during chemotherapy, cytostatic molecules like Rapa would require repeat administrations in clinical settings. To optimize FKBP/Rapa for subcutaneous (SC) administration, this manuscript expands upon first-generation FSI nanoparticles ( R h ~ 25 nm) and compares them with two second-generation carriers (FA and FAF) that: i) do not self-assemble; ii) retain a hydrodynamic radius ( R h ~ 7 nm) above the renal filtration cutoff; iii) increase tumor accumulation; and iv) have either one (FA) or two (FAF) drug-binding FKBP domains per ELP protein.
Methods: The carriers were compared and evaluated for temperature-concentration phase behavior by UV-Vis spectrophotometry; equilibrium binding and thermodynamics by Isothermal Titration Calorimetry; drug retention and formulation stability by Dialysis and Dynamic Light Scattering; in vitro efficacy using a cell proliferation assay; in vivo efficacy in human MDA-MB 468 orthotopic breast cancer xenografts; downstream target inhibition using western blot; tissue histopathology; and bio-distribution via optical imaging in the orthotopic xenograft mouse model.
Results: Named after the two-headed bird in Hindu mythology, the ‘Berunda polypeptide’ FAF with molecular weight of 97 kDa and particle size, R h ~ 7 nm demonstrated polypeptide conformation of a soluble hydrated coiled polymer, retained formulation stability for one month post Rapa loading, eliminated toxicity observed with free Rapa after SC administration, suppressed tumor g rowth, decreased phosphorylation of a downstream target, and increased tumor accumulation in orthotopic breast tumor xenografts.
Conclusion: This comprehensive manuscript demonstrates the versatility of recombinant protein-polymers to investigate drug carrier architectures. Furthermore, their facilitation of SC administration of poorly soluble drugs, like Rapa, may enable chronic self-administration in patients.

Keywords elastin-like polypeptides, rapamycin, triple negative breast cancer, drug delivery, bio-distribution, optical imaging

Theranostics 2017; 7(16):3856-3872.

Selected Publications

Learn more...

Berunda Polypeptides: Multi-Headed Fusion Proteins Promote Subcutaneous Administration of Rapamycin to Breast Cancer In Vivo

Ocular Drug Delivery

Antibody Nanoworms

Cognate Drug Receptors

Intracellular Switches