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Observational Study
. 2022 Feb;52(2):265-275.
doi: 10.1111/cea.14087. Epub 2022 Jan 14.

Cat allergen exposure in a naturalistic exposure chamber: A prospective observational study in cat-allergic subjects

William H Yang  1 , Suzanne Kelly  1 , Laura Haya  1 , Rym Mehri  1 , Divya Ramesh  2 , Michelle DeVeaux  2 , Claire Q Wang  2 , Pretty Meier  2 , Sumit Narula  2 , Furat Shawki  2 , Ryan Pennington  2 , Lorah Perlee  2 , Meagan P O'Brien  2
Affiliations
Observational Study

Cat allergen exposure in a naturalistic exposure chamber: A prospective observational study in cat-allergic subjects

William H Yang et al. Clin Exp Allergy. 2022 Feb.

Abstract

Background: To determine the proportion and reproducibility of cat-allergic mild asthmatics with early asthmatic response (EAR) during cat allergen exposure in a naturalistic exposure chamber (NEC).

Methods: This was a prospective, observational study in 30 cat-allergic mild asthmatics who received two 180-min cat-allergen (Felis domesticus allergen 1 [Fel d 1]) challenges 27 days apart in an NEC.

Results: An EAR (≥20% reduction from baseline in forced expiratory volume in 1 s [FEV1]) was observed in 67% and 52% of subjects at first and second NEC exposure, respectively, with similar median time to EAR; 44% of subjects had an EAR on days 1 and 28. Late asthmatic response (≥15% reduction in FEV1 within 24 h of NEC exit) was observed in 33% of subjects following either exposure. Average FEV1 and total nasal symptom score during NEC exposure were highly correlated within subjects between NEC exposures (r = 0.91, p < 0.0001; r = 0.73, p < 0.001), but total ocular symptom score was not. Time to EAR, but not average FEV1, was significantly associated with NEC Fel d 1 concentration, which was variable. There were no serious adverse events; 12/30 subjects experienced 20 adverse events (including asthma, 10%; headache, 10%).

Conclusions: The NEC model demonstrates that average FEV1 change is highly reproducible and has a low correlation with cat allergen levels. However, time to EAR and incidence of EAR are less reproducible and are highly correlated with NEC allergen levels. Average FEV1, rather than incidence of EAR or time to EAR, could be considered as an endpoint for interventional trials testing cat-specific anti-allergy therapies using an NEC.

Keywords: allergy treatment; asthma; challenge tests.

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Conflict of interest statement

William H. Yang is a stockholder and employee of Red Maple Trials, Inc. He has received consultant and speaker fees from CSL Behring, Shire/Takeda, Novartis, Sanofi, Merck; and research grants from CSL Behring, Shire/Takeda, BioCryst, Pharvaris, Sanofi, Regeneron Pharmaceuticals, Inc., GSK, AstraZeneca, Amgen, Genentech/Roche, Pfizer, ALK, Stallergenes, Providence, Galderma, Glenmark, Dermira and AnaptysBio. Suzanne Kelly is a stockholder and employee of Red Maple Trials, Inc. Laura Haya is an employee of Red Maple Trials, Inc. Rym Mehri has received grant contribution from Red Maple Trials, Inc. and Mitacs Canada. D. Ramesh, M. DeVeaux, P. Meier, S. Narula, F. Shawki, C.Q. Wang, R. Pennington, L. Perlee and M . P. O’Brien are stockholders and employees of Regeneron Pharmaceuticals, Inc.

Figures

FIGURE 1
FIGURE 1
Study design, subject disposition and NEC set up. NEC, naturalistic exposure chamber. *Two subjects with unreliable spirometry data were excluded from spirometry‐related analyses
FIGURE 2
FIGURE 2
(A) Proportion of subjects experiencing an EAR in the NEC and (B) median time to EAR at days 1 and 28 following NEC challenge. EAR, early asthmatic response; Fel d 1, Felis domesticus allergen 1; NEC, naturalistic exposure chamber. “Day 1 or day 28” represents the proportion of subjects who experienced an EAR on either day 1 or day 28, but not both. Dotted line corresponds to the median time to EAR on days 1 and 28
FIGURE 3
FIGURE 3
FEV1 during day 1 and day 28 NEC exposure. FEV1, forced expiratory volume in 1 s; NEC, naturalistic exposure chamber; SE, standard error. Top plot shows the mean FEV1 (±SE) across subjects every 10 min for each NEC exposure. Middle plot shows the correlation of average FEV1 on day 1 vs. day 28, with Pearson correlation coefficient, p‐value and the line of best fit (linear least squares). Lower plot shows the average FEV1 per subject on day 1 vs. day 28; the lines connect the values for the same subject
FIGURE 4
FIGURE 4
(A) Fel d 1 concentration during NEC exposure and, (B) and (C), association between time to EAR and Fel d 1 concentration in the NEC. C, concentration; EAR, early asthmatic response; Fel d 1, Felis domesticus allergen 1; m, collected mass, NEC, naturalistic exposure chamber; Q, pump flow rate (typically 0.004 m3/min); SD, standard deviation; t, challenge duration. The calculated subject pump Fel d 1 air concentration in ng/m3 is averaged over the challenge duration: C = m/(Q*t). The calculated room pump Fel d 1 air concentration in ng/m3 averaged over the challenge duration, collected from the pump cartridge(s) suspended in the room nearest the subject, was C = m/(Q*t)
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