The average total TNSS included the evaluation of 4 nasal symptoms: itchy nose, blocked nose, runny nose, and sneezing. The endpoint was based on participant diary entries over the last 4 hours of the EEC challenge session at Week 24. TNSS was the total of scores for the 4 nasal symptoms, each scored on a 4-point rating scale (0=no symptoms; 1=mild symptoms; 2=moderate symptoms; 3=severe symptoms). The total TNSS ranged from 0 to 12 points. The 24-week TNSS was analyzed using the analysis of covariance (ANCOVA) model with treatment and baseline TNSS as covariates and expressed as a least squares mean with 95% confidence interval. A decrease in TNSS for participants receiving either dose of MK-8237 compared to placebo indicated an improvement in symptoms.

Full Analysis Set including all randomized participants who received at least one dose of study treatment and had at least one post-randomization measurement for the analysis endpoint

The average total TNSS included the evaluation of 4 nasal symptoms: itchy nose, blocked nose, runny nose, and sneezing. The endpoint was based on participant diary entries over the last 4 hours of the EEC challenge session at Week 16. TNSS was the total of scores for the 4 nasal symptoms, each scored on a 4-point rating scale (0=no symptoms; 1=mild symptoms; 2=moderate symptoms; 3=severe symptoms). The total TNSS ranged from 0 to 12 points. The Week 16 TNSS was analyzed using the ANCOVA model with treatment and baseline TNSS as covariates and expressed as a least squares mean with 95% confidence interval. A decrease in TNSS for participants receiving either dose of MK-8237 compared to placebo indicated an improvement in symptoms.

Full Analysis Set including all randomized participants who received at least one dose of study treatment and had at least one post-randomization measurement for the analysis endpoint

The average total TNSS included the evaluation of 4 nasal symptoms: itchy nose, blocked nose, runny nose, and sneezing. The endpoint was based on participant diary entries over the last 4 hours of the EEC challenge session at Week 8. TNSS was the total of scores for the 4 nasal symptoms, each scored on a 4-point rating scale (0=no symptoms; 1=mild symptoms; 2=moderate symptoms; 3=severe symptoms). The total TNSS ranged from 0 to 12 points. The Week 8 TNSS was analyzed using the ANCOVA model with treatment and baseline TNSS as covariates and expressed as a least squares mean with 95% confidence interval. A decrease in TNSS for participants receiving either dose of MK-8237 compared to placebo indicated an improvement in symptoms.

Full Analysis Set including all randomized participants who received at least one dose of study treatment and had at least one post-randomization measurement for the analysis endpoint

The average total TSS included the evaluation of the 4 nasal symptoms of the TNSS (itchy nose, blocked nose, runny nose, and sneezing) plus the 2 ocular symptoms of the TOSS (gritty/feeling/red/itchy eyes and watery eyes). The endpoint was based on participant diary entries over the last 4 hours of the EEC challenge session at Week 24. TSS was the total of scores for the 4 nasal symptoms and 2 ocular symptoms, each scored on a 4-point rating scale (0=no symptoms; 1=mild symptoms; 2=moderate symptoms; 3=severe symptoms). The total TSS ranged from 0 to 18 points. The Week 24 TSS was analyzed using the ANCOVA model with treatment and baseline TSS as covariates and expressed as a least squares mean with 95% confidence interval. A decrease in TSS for participants receiving either dose of MK-8237 compared to placebo indicated an improvement in symptoms.

Full Analysis Set including all randomized participants who received at least one dose of study treatment and had at least one post-randomization measurement for the analysis endpoint

The average total TSS included the evaluation of the 4 nasal symptoms of the TNSS (itchy nose, blocked nose, runny nose, and sneezing) plus the 2 ocular symptoms of the TOSS (gritty/feeling/red/itchy eyes and watery eyes). The endpoint was based on participant diary entries over the last 4 hours of the EEC challenge session at Week 16. TSS was the total of scores for the 4 nasal symptoms and 2 ocular symptoms, each scored on a 4-point rating scale (0=no symptoms; 1=mild symptoms; 2=moderate symptoms; 3=severe symptoms). The total TSS ranged from 0 to 18 points. The Week 16 TSS was analyzed using the ANCOVA model with treatment and baseline TSS as covariates and expressed as a least squares mean with 95% confidence interval. A decrease in TSS for participants receiving either dose of MK-8237 compared to placebo indicated an improvement in symptoms.

Full Analysis Set including all randomized participants who received at least one dose of study treatment and had at least one post-randomization measurement for the analysis endpoint

The average total TSS included the evaluation of the 4 nasal symptoms of the TNSS (itchy nose, blocked nose, runny nose, and sneezing) plus the 2 ocular symptoms of the TOSS (gritty/feeling/red/itchy eyes and watery eyes). The endpoint was based on participant diary entries over the last 4 hours of the EEC challenge session at Week 8. TSS was the total of scores for the 4 nasal symptoms and 2 ocular symptoms, each scored on a 4-point rating scale (0=no symptoms; 1=mild symptoms; 2=moderate symptoms; 3=severe symptoms). The total TSS ranged from 0 to 18 points. The Week 8 TSS was analyzed using the ANCOVA model with treatment and baseline TSS as covariates and expressed as a least squares mean with 95% confidence interval. A decrease in TSS for participants receiving either dose of MK-8237 compared to placebo indicated an improvement in symptoms.

Full Analysis Set including all randomized participants who received at least one dose of study treatment and had at least one post-randomization measurement for the analysis endpoint

The average total TOSS included the evaluation of 2 ocular symptoms: gritty/feeling/red/itchy eyes and watery eyes. The endpoint was based on participant diary entries over the last 4 hours of the EEC challenge session at Week 24. TOSS was the total of scores for the 2 ocular symptoms, each scored on a 4-point rating scale (0=no symptoms; 1=mild symptoms; 2=moderate symptoms; 3=severe symptoms). The total TOSS ranged from 0 to 6 points. The Week 24 TOSS was analyzed using the ANCOVA model with treatment and baseline TOSS as covariates and expressed as a least squares mean with 95% confidence interval. A decrease in TOSS for participants receiving either dose of MK-8237 compared to placebo indicated an improvement in symptoms.

Full Analysis Set including all randomized participants who received at least one dose of study treatment and had at least one post-randomization measurement for the analysis endpoint

The average total TOSS included the evaluation of 2 ocular symptoms: gritty/feeling/red/itchy eyes and watery eyes. The endpoint was based on participant diary entries over the last 4 hours of the EEC challenge session at Week 16. TOSS was the total of scores for the 2 ocular symptoms, each scored on a 4-point rating scale (0=no symptoms; 1=mild symptoms; 2=moderate symptoms; 3=severe symptoms). The total TOSS ranged from 0 to 6 points. The Week 16 TOSS was analyzed using the ANCOVA model with treatment and baseline TOSS as covariates and expressed as a least squares mean with 95% confidence interval. A decrease in TOSS for participants receiving either dose of MK-8237 compared to placebo indicated an improvement in symptoms.

Full Analysis Set including all randomized participants who received at least one dose of study treatment and had at least one post-randomization measurement for the analysis endpoint

The average total TOSS included the evaluation of 2 ocular symptoms: gritty/feeling/red/itchy eyes and watery eyes. The endpoint was based on participant diary entries over the last 4 hours of the EEC challenge session at Week 8. TOSS was the total of scores for the 2 ocular symptoms, each scored on a 4-point rating scale (0=no symptoms; 1=mild symptoms; 2=moderate symptoms; 3=severe symptoms). The total TOSS ranged from 0 to 6 points. The Week 8 TOSS was analyzed using the ANCOVA model with treatment and baseline TOSS as covariates and expressed as a least squares mean with 95% confidence interval. A decrease in TOSS for participants receiving either dose of MK-8237 compared to placebo indicated an improvement in symptoms.

Full Analysis Set including all randomized participants who received at least one dose of study treatment and had at least one post-randomization measurement for the analysis endpoint

Dermatophagoides pteronyssinus (D. pteronyssinus) and Dermatophagoides farinae (D. farinae) serum IgE levels were measured using the Immunocap® assay at Week 8. IgE levels were expressed in Log 10 scale kilo units/Liter (kU/L). Analysis was based on the analysis of variance parametric (ANOVA) model with treatment as the fixed effect and reported as mean IgE with a standard deviation.

Full Analysis Set including all randomized participants who received at least one dose of study treatment and had at least one post-randomization measurement for the analysis endpoint

D. pteronyssinus and D. farinae serum IgG4 levels were measured using the Immunocap® assay at Week 8. IgG4 levels were expressed in Log 10 scale milligrams/Liter (mg/L). Analysis was based on the ANOVA model with treatment as the fixed effect and reported as mean IgG4 with a standard deviation.

Full Analysis Set including all randomized participants who received at least one dose of study treatment and had at least one post-randomization measurement for the analysis endpoint

D. pteronyssinus and D. farinae serum IgE levels were measured using the Immunocap® assay at baseline and Week 8. IgE levels were expressed in Log 10 scale kU/L. Mean Week 8 IgE levels were compared to the mean IgE levels at baseline. Analysis was based on the ANOVA model with treatment as the fixed effect and reported as a least squares mean with 95% confidence interval.

Full Analysis Set including all randomized participants who received at least one dose of study treatment and had at least one post-randomization measurement for the analysis endpoint

D. pteronyssinus and D. farinae serum IgG4 levels were measured using the Immunocap® assay at baseline and Week 8. IgG4 levels were expressed in Log 10 scale mg/L. Mean Week 8 IgG4 levels were compared to the mean IgG4 levels at baseline. Analysis was based on the ANOVA model with treatment as the fixed effect and reported as a least squares mean with 95% confidence interval.

Full Analysis Set including all randomized participants who received at least one dose of study treatment and had at least one post-randomization measurement for the analysis endpoint

An AE was defined as any untoward medical occurrence in a participant administered a pharmaceutical product and which did not necessarily have to have a causal relationship with this treatment. An AE could therefore be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal product/protocol-specified procedure, whether or not considered related to the medicinal product/protocol-specified procedure. Any worsening of a preexisting condition temporally associated with the use of the product was also an AE. A serious adverse event (SAE) was an AE that resulted in death, was life threatening, resulted in persistent or significant disability/incapacity, resulted in or prolonged an existing inpatient hospitalization, was a congenital anomaly/birth defect, was a cancer, was associated with an overdose, was another important medical event.

All Participants as Treated including all randomized participants who received at least one dose of study treatment

The percentage of participants who had study treatment stopped due to an AE. Discontinuations were reported for all randomized participants who received ≥1 dose of study treatment.

All Participants as Treated including all randomized participants who received at least one dose of study treatment