Hyaluronan-Lysine Cisplatin Drug Carrier for Treatment of Localized Cancers: Pharmacokinetics, Tolerability, and Efficacy in Rodents and Canines

Abstract

The purpose of this study was to develop a safe and efficacious drug delivery platform for sustained release of cisplatin after locoregional administration. We successfully synthesized hyaluronan-cisplatin nanoconjugates (HA-Lys-Pt) using an N-Ac-lysine linker, which formed a thermodynamically stable 5-membered ring with the platinum. The conjugate was characterized for release kinetics, in vitro anti-proliferative activity, degradability, impurity content, formation of Pt-DNA adducts, pharmacokinetics, tolerability in rodents and canines, and for efficacy in rodents. The 75kD HA-Lys-Pt (75HALys-Pt) sustained release of platinum with a 69 hour half-life in phosphate buffered saline without substantial burst release. Compared to intravenous cisplatin, subcutaneously injected 75HA-Lys-Pt formed 3.2-fold more Pt-DNA adducts in rat peripheral blood mononuclear cells compared to intravenous cisplatin over 96 hours. Subcutaneous 75HA-Lys-Pt was tolerable in rats at 40 mg/kg (4× the LD50 of conventional cisplatin) and resulted in 62.5% partial response and 37.5% stable disease in murine xenografts of head and neck squamous cell cancer (20 mg/kg/wk × 3 wk). 75HA-Lys-Pt demonstrated extended tmax and improved area-under-the-curve compared to cisplatin in rats and canines. Canine safety was demonstrated by liver enzyme and electrolyte levels, complete blood count, and urinalysis.

Formation of platinum (II) as a six member ring for sustained polymeric delivery

“…The pHP group was removed by photolysis in water at ~300–350 nm. The resulting photoproducts were removed by dialysis to afford HA-Ac-Lys 6 , which was then converted to the HA-Ac-Lys-Pt conjugate 7 at 50°C, using cisplatin (diaqua form) as reported previously [6]. …”

“…The reaction mixture of conjugate 15 required several more additions of NaOH over 48 h to maintain a pH of ca. 5, whereas the reaction pH of conjugate 7 was nearly constant for 36 h. The Pt loading degrees of conjugates 7 and 15 were determined to be 5% and 6%, respectively, by inductively coupled plasma mass spectrometry (Agilent 7500a ICP-MS, method described in [6]).…”

“…Previously we reported that HA-Ac-Lys could be utilized to conjugate cisplatin forming a robust five-membered ring with the COOH group and nitrogen of N-acetyl group of lysine linker [6]. However, this method involved the reaction between HA-tetrabutylammonium salt and N-Ac-Lys in DMSO, which is difficult to scale up and time-consuming to purify.…”

“…Release studies of platinum species from HA-Lys-Pt [6] and HA-homo-Lys-Pt were evaluated via dialysis against PBS at the physiological pH of 7.4 at 37 °C and against acetate buffer at pH 5.5 to mimic the acidic environment of tumor cells, which is normally 6.5–6.8 (normal physiological pH is 7.3–7.4) but may be < pH 5 in necrotic regions [14]. The platinum concentrations in dialysis bag were measured and plotted as the percentage of cumulative drug released against time (Figure 3).…”

“…Conventional platinum therapies are given intravenously, which results in the rapid clearance of the drug from the body and minimum retention in diseased organs. We have a longstanding interest in developing strategies for targeted delivery and the controlled release of cancer drugs including cisplatin [6, 7]. Our previous studies have shown that sustained released drug delivered by nanocarriers via local regional injection demonstrated superior pharmacokinetics, reduced side effects and significantly improved anti-cancer efficacy in various mouse xenografts and naturally occurring canine cancers.…”