Bioavailability of protein therapeutics in rats following inhalation exposure: Relevance to occupational exposure limit calculations.

Protein therapeutics represent a rapidly growing proportion of new medicines being developed by the pharmaceutical industry. As with any new drug, an Occupational Exposure Limit (OEL) should be developed to ensure worker safety. Part of the OEL determination addresses bioavailability (BA) after inhalation, which is poorly understood for protein therapeutics. To explore this, male Sprague-Dawley rats were exposed intravenously or by nose-only inhalation to one of five test proteins of varying molecular size (10-150 kDa), including a polyethylene glycol-conjugated protein. Blood, lung tissue and bronchoalveolar lavage (BAL) fluid were collected over various time-points depending on the expected test protein clearance (8 minutes-56 days), and analyzed to determine the pharmacokinetic profiles. Since the BAL half-life of the test proteins was observed to be > 4.5 h after an inhalation exposure, accumulation and direct lung effects should be considered in the hazard assessment for protein therapeutics with lung-specific targets. The key finding was the low systemic bioavailability after inhalation exposure for all test proteins (∼≤1%) which did not appear molecular weight-dependent. Given that this study examined the inhalation of typical protein therapeutics in a manner mimicking worker exposure, a default 1% BA assumption is reasonable to utilize when calculating OELs for protein therapeutics.

Use of low-dose clinical pharmacodynamic and pharmacokinetic data to establish an occupational exposure limit for dapagliflozin, a potent inhibitor of the renal sodium glucose co-transporter 2.

Classical risk assessment models for setting safe occupational exposure limits (OEL) have used multiple uncertainty factors (UF) applied to a point of departure (POD), e.g., a No Observed Effect Level (NOEL), which in some cases is the pharmacological effect. Dapagliflozin promotes glucosuria by inhibiting the renal sodium-glucose cotransporter-2 transporter. The initial OEL for dapagliflozin (0.002mg/m(3)) was calculated when low dose clinical data was not available to identify a NOEL resulting in the need to use excessive UFs. To reduce the UFs from the OEL, a clinical pharmacodynamic [glucosuria and urinary glucose dipstick (UGD)] and pharmacokinetic study was conducted with single oral doses of 0.001, 0.01, 0.1, 0.3, 1.0 or 2.5mg administered to 36 healthy subjects. Dose-related dapagliflozin systemic exposures were observed at doses ⩾0.1mg and glucosuria was observed at doses ⩾0.3mg and corroborated by UGD. The NOEL was therefore 0.1mg for glucosuria. For setting the new OEL, no UFs were required. Dividing the POD by 10m(3) (the volume of air an adult inhales in a workday), the resulting OEL was 0.01mg/m(3). In conclusion, low-dose clinical pharmacodynamic and pharmacokinetic data can allow the OEL to be adjusted to the highest safe level.

Hazard identification of strong dermal sensitizers.

Dermal reactions are the most frequently reported chemical health-related occupational hazard. Identifying dermal sensitizers is important for improving workplace safety. This paper takes a close look at the physico-chemical properties and results from the Local Lymph Node Assay (LLNA) to better understand and predict potent dermal sensitizers. The LLNA was used to identify 28 pharmaceutical agents or chemical intermediates as potent dermal sensitizers, EC3 < 1%. Certain parameters were examined to determine if there was any predictability to identify potent dermal sensitizers. These included a computer structure activity analysis using Derek for Windows, molecular weight (Mw), calculated log P, and the log-linear extrapolation approach for estimating the potency. With Derek for Windows, 13 compounds were identified as negative and 15 as positive for structural alerts, the most common being haloalkanes, and hydrazines. Additional mechanisms of reactivity were postulated for the remaining compounds. The examination of the Mw showed that all molecules had Mw < 550 Da. For 21 compounds, the interpolated vs extrapolated methods for determining the EC3 value were compared. For eight of the 21 compounds, the extrapolated EC3 was in the correct order of magnitude, eight were incorrect (five were too high and three were too low) and five could not be calculated. The use of a tiered approach including examination of the structural and physico-chemical properties and the LLNA to identify potent dermal sensitizers is integral in the selection of effective safe handling guidance to protect from sensitization hazards.