OFM-recirculation and OFM-suction: advanced in-vivo open flow microperfusion (OFM) methods for direct and absolute quantification of albumin in interstitial fluid

Abstract

Objective: To implement OFM-recirculation and OFM-suction capable of direct and absolute in-vivo quantification of albumin in the ISF of pigs. Approach: OFM-recirculation and OFM-suction were used to collect ISF in-vivo in pigs and lymph was collected from the same pigs after OFM sampling. Blood was collected before and after OFM sampling, plasma was isolated and mean albumin plasma concentrations per pig were used to yield albumin ISF-to-plasma ratios. We characterized the quality of the collected undiluted ISF via (1) stable albumin ISF-to-plasma ratio in OFM-recirculation and in OFM-suction samples, (2) comparison of albumin ISF-to-plasma ratios from OFM-recirculation and OFM-suction and (3) comparison of normalized albumin concentrations in the ISF and lymph. Main results: Both advanced OFM methods were successfully implemented and albumin was quantified from the collected ISF samples. OFM-recirculation reached stable albumin ISF-to-plasma ratios after 20 recirculation cycles. Absolute ISF albumin concentrations were 11.2 mg ml−1 (OFM-recirculation) and 14.2 mg ml−1 (OFM-suction). Albumin ISF-to-plasma ratios were 0.39 ± 0.04 (OFM -recirculation) and 0.47 ± 0.1 (OFM-suction). Significance: Knowledge of the ISF protein content is of major importance when assessing PK/PD effects, especially of highly protein bound drugs. Up to now, only blood albumin values have been available to determine the degree of protein binding in several tissues. OFM-recirculation and OFM-suction allow direct, absolute quantification of albumin in ISF for the first time and enable investigation of the degree of protein binding of a drug directly in its target tissue.

Comparative Study of Dermal Pharmacokinetics Between Topical Drugs Using Open Flow Microperfusion in a Pig Model

“…In Study#2 the dISF concentration of brepocitinib following the brepocitinib 3% cream BID application was assessed at two application sites in two different ways: first via dOFM standard sampling and mathematical correction for the dilution, and second via an recirculation approach directly delivering undiluted dISF (for more details see Hummer et al . [ 45 ]). For the recirculation approach, the outflow of the dOFM probe was connected to the inflow of the probe via the peristaltic pump tubing such that the perfusate of approx.…”

Characterizing the Pharmacokinetics and Biodistribution of Therapeutic Proteins: An Industry White Paper

“…Alternatively, in vivo biodistribution may be measured in the intact animal via radiolabeling or fluorescence conjugation, and then measured by positron emission tomography (PET), immunofluorescence, or other imaging techniques (Williams, 2012). More recently, large-pore microdialysis or open flow microperfusion have also emerged as minimally invasive techniques to measure the time course of tissue or tumor interstitial fluid concentrations of TPs (Hummer et al, 2021). It is important to thoroughly understand the advantages and limitations of each analytical technique; e.g.…”

Dermal open flow microperfusion for PK-based clinical bioequivalence studies of topical drug products

“…Both, ABE and SABE have been successfully used to analyze dOFM data (Bodenlenz et al, 2017;Tiffner et al, 2020) Strengths of dOFM for PK-based BE studies dOFM can be used to sample any API regardless of its molecular size or structure or the formulation that is used for its delivery. dOFM has already been successfully used to sample lipophilic (Bodenlenz et al, 2012;Holmgaard et al, 2012;Bodenlenz et al, 2016), high-molecular-weight (Dragatin et al, 2016;Kolbinger et al, 2017) and hydrophilic APIs with low skin permeation ability (Bodenlenz et al, 2017), bound and unbound drugs, peptides, proteins, antibodies, and APIs with high-protein-binding properties (Dragatin et al, 2016;Kolbinger et al, 2017;Hummer et al, 2020;Tiffner et al, 2020). dOFM samples reflect the molecular composition of the ISF because sampling collects diluted but unfiltered dermal ISF.…”