Clinical benefits with 300 IR HDM SLIT tablet in Europeans with house dust mite allergic rhinitis: Post hoc analysis of a large phase 3 trial

Background House dust mite (HDM)-induced allergic rhinitis (AR) is a major cause of allergic respiratory disease. The efficacy and safety of the 300 IR HDM sublingual immunotherapy (SLIT) tablet in patients with moderate-to-severe HDM-AR was confirmed in a large, international, phase 3 randomized controlled trials (RCTs). Here, we analyzed the results in the European population. Methods Data from 91 European centers that participated in the international, double-blind, RCT (EudraCT 2014-004223-46, NCT02443805) with the 300 IR HDM SLIT tablet versus placebo over 12 months were analyzed post hoc. The treatment effect in European adults and adolescents was notably assessed through the European Academy of Allergy and Clinical Immunology (EAACI)-recommended combined symptom and medication score (CSMS0-6, pre-defined endpoint) and the total combined rhinitis score (TCRS0-24, post hoc endpoint, also balanced) during the primary evaluation period (4 weeks at the end of treatment period) using analysis of covariance (ANCOVA). Results There were 818 patients who comprised the modified full analysis set in Europe. Over the primary period, the differences in CSMS0-6 and TCRS0-24 between the 300 IR and placebo groups were statistically significant (p < 0.0001): −0.32 (95%CI [-0.46; −0.17]) and −1.28 (95%CI [-1.63; −0.94]), respectively, with relative differences of −20.9% and −21.2%. All post hoc and the rhinoconjunctivitis quality of life endpoints were significantly improved with 300 IR versus placebo. The 300 IR HDM tablet was generally well tolerated. Conclusion This RCT sub-analysis confirmed the 300 IR HDM SLIT tablet is an effective and safe treatment for European adults and adolescents with HDM-AR with clinically meaningful benefits from the patients' perspective. Trial registration NCT02443805. Registered on April 29, 2015./EudraCT 2014-004223-46. Registered on September 16, 2015.


BACKGROUND
Allergic rhinitis (AR)/rhinoconjunctivitis (ARC) is a disorder of the nose and eyes affecting about one-fifth of the general population primarily driven by an immunoglobulin E (IgE)-mediated type I hypersensitivity response, due to an allergen exposure. 1,210][11] Medical treatment of AR aiming at eliminating both symptoms and inflammatory reactions is mainly based on antihistamines, nasal steroids, or leukotriene receptor antagonists, but symptom relief does not extend beyond the end of treatment. 125][26][27][28] Of these, the most recent, international, phase 3 pivotal RCT confirmed the benefits of a 12-month course of treatment with the 300 IR HDM SLIT tablet versus placebo in a large population of adults and adolescents. 25In this trial, the primary endpoint was the average total combined score (TCS, scale 0-15), defined as the sum of the patient's daily rhinitis total symptom score (RTSS, scale 0-12) and daily rescue medication score (RMS, scale 0-3), during 4 weeks at the end of the treatment period.The primary endpoint was met with a difference in total combined score (TCS) of À16.9% between the 300 IR and placebo groups.The pre-specified secondary endpoints consistently confirmed this result demonstrating the robustness of outcomes.
The aim of this post hoc analysis was the evaluation of the European Union (EU) patients that participated in this international trial 25 to analyze the possible impact of differences in clinical management and/or in patients' monitoring between regions in addition to possible intrinsic differences between patients from various regions.Moreover, the treatment effect of the 300 IR HDM SLIT tablet in this EU subpopulation primarily assessed on the imbalanced TCS 0-15 was compared with that on 2 combined scores equally weighing symptom and medication scores as recommended by Health Authorities and international experts: 29,30 i) the European Academy of Allergy and Clinical Immunology (EAACI)-proposed total combined symptom and medication score (CSMS 0-6 , a pre-defined endpoint) and ii) the total combined rhinitis score (TCRS 0-24 , a post hoc endpoint).Further insight into how this treatment effect can be translated into a clinically relevant improvement perceivable by the patients is also provided.

Study design and materials
The study design, set up, and results of the large, international, double-blind, placebocontrolled, phase 3 trial (EudraCT 2014-004223-46 and ClinicalTrials.govNCT 02443805) have already been published. 25Here we report the results observed in the 91 centers from 9 EU countries involved in the trial: Belgium, Bulgaria, Czech Republic, France, Germany, Italy, Poland, Slovakia, and Spain.
Briefly, the screening phase lasted 6 weeks to 6 months (including a 5-week, single-blind, placebo run-in period), the double-blind treatment phase for approximately 12 months, and the follow-up period around 2 weeks.Patients with an average TCS of 5 or more out of 15 over the last 4 weeks of the 5-week run-in period were centrally randomized 1:1 (computer-generated randomization with stratification by study site per participating country) to receive HDM AIT (a sublingual tablet formulation of standardized, purified, freeze-dried, sieved D. pteronyssinus and D. farinae extracts for daily administration; allergen content per 300 IR formulation: 14-17 mg Der p 1 and 53-68 mg Der f 1; Stallergenes Greer, Antony, France) or placebo.During the dose escalation phase, patients received a 100 IR tablet on Day 1 (under medical supervision for 30 min), 2 100 IR tablets on Day 2, and a 300 IR tablet on Day 3, or matching placebo tablets.The maintenance treatment consisted of 300 IR tablet or placebo once daily.

Trial population
The main inclusion criteria were reported previously. 25Briefly, the population ranged from 12 to 65 years, had physician-diagnosed HDM-induced AR with or without concomitant asthma, and proven sensitization to D. pteronyssinus and/or D. farinae (skin prick test !5 mm than negative control and specific serum IgE !3.5 kU/L).The main exclusion criteria followed the guidelines, notably confounding allergies during the 4-week primary evaluation period, partly controlled or uncontrolled asthma according to Global Initiative for Asthma (GINA) 2014 classification, 31 previous AIT and the standard contraindications to AIT.

Ethics approval and consent to participate
This double-blind, placebo-controlled, randomized clinical trial was performed in accordance with good clinical practice defined by the International Council for Harmonization and the principles that have their origin in the Declaration of Helsinki and local laws and regulations.All participants or parents or legal representatives (for participants 17 years or younger) gave their written consent to participation, after having been informed of the trial objectives and procedures.

Endpoints
As previously described, the primary endpoint of the main study was the average of the daily TCS during the 4-week primary evaluation period.The daily TCS 0-15 was the sum of the patient's daily RTSS 0-12 and the daily RMS 0-3 .One of the key predefined secondary endpoints of this RCT was the CSMS 0-6 calculated as RTSS 0-12 /4 þ RMS 0-3, thus equally weighing the symptom severity and rescue medication use as recommended by the European Medicines Agency (EMA) 30 and the EAACI. 29It is worth noting that the RMS component of both TCS and CSMS used a stepwise approach endorsed by both Health Authorities and international experts, scoring 0 for no treatment, 1 for an oral H1 antihistamine, 2 for intranasal corticosteroid, and 3 for oral corticosteroid. 29,30ased on previously published scores, 32 an alternate daily medication score (DMS) was analyzed post hoc imputing a score of 4 per tablet of oral antihistamine (maximum daily score ¼ 4), a score of 2 per puff of intranasal corticosteroid (maximum daily score ¼ 8, ie, 2 puffs per nostril) and, if applicable, a score of 12 on the day of oral corticosteroid intake.The DMS ranged from 0 to 12.A second balanced combined score, TCRS calculated as RTSS 0- subgroup of EU patients and compared with the imbalanced TCS 0-15 and the results in the overall population.
Other clinical endpoints of the main trial were also analyzed post hoc in the EU subpopulation: RTSS, RMS, rhinoconjunctivitis total symptom score (RCTSS), 6 individual rhinoconjunctivitis symptom scores (ISSs), total ocular symptom score (TOSS), rhinoconjunctivitis quality of life questionnaire (RQLQ) score, and safety variables.

Clinical relevance
Based on the CSMS 0-6 , the treatment effect (ie, the reduction in symptom and medication score with the 300 IR HDM tablet versus placebo over the primary period) was translated into a clinically relevant improvement from the patients' perspective by considering either component of the combined score: RTSS 0-12 or RMS 0-3 .The reduction in RTSS 0-12 was correlated to a decrease in symptom severity while the reduction in RMS 0-3 was correlated to a decrease in the number of days with less therapy for a patient taking antihistamines or nasal corticosteroids daily over the time period.

Statistical analysis
Data were analyzed with the same methodology used in the main study. 25 definition, the modified full analysis set (mFAS) comprised all participants who received at least one dose of the investigated product (IP) and had at least one evaluation of the primary variable during the primary evaluation period.
The baseline period was defined as the last 4 weeks of the 5-week run-in period and the primary evaluation period as the 4 weeks preceding the last record within a time window of last IP AE 28 days for patients treated at least 300 days.The ANCOVA model for appropriate assessment scores (TCS, CSMS, TCRS, RTSS, RMS, RCTSS, ISSs, and TOSS) was executed on the square root of the average score during the primary evaluation period with treatment group as main effect, and the pooled center, square root of the baseline average score, gender, age, asthma and sensitization status as covariates; p-values were twosided.The back-transformed least squares (LS) means for each treatment group were used to assess the absolute (point estimate) and relative LS mean differences, with the relative LS mean difference (%) ¼ 100 x [(LS mean 300 IR -LS mean placebo)/LS mean placebo].
For the quality-of-life endpoint analysis (RQLQ score), the ANCOVA model did not used the square root transformation.
Additional models for a subgroup analysis of CSMS and TCRS have been performed by adding interaction between the treatment group and the subgroup of patients with "at least one rescue medication use at baseline".
A Mixed Model with Repeated Measures has been used to assess the treatment effect at study timepoints (3 months, 6 months, 9 months, 12 months) by adding timepoint effect and the interaction between treatment group and timepoint.
The safety analysis was conducted on the safety set comprising all randomized patients having received at least 1 dose of the IP.
Statistical analyses were performed with SAS software (version 9.4, SAS Institute, Inc, Cary, NC).

Study patients
Of the 1607 adults and adolescents randomized in this trial, 992 were recruited in European centers and treated either with the 300 IR HDM tablet (N ¼ 498) or with placebo (N ¼ 494).The modified full analyisis set (mFAS) comprised 818 EU patients (384 in the 300 IR group and 434 in the placebo group).
There were no differences between the 300 IR and placebo groups regarding baseline sociodemographic variables, clinical characteristics, and sensitization status of this subpopulation (Table 1).
Baseline symptom and medication scores were similar in both treatment groups (Supplemental In the safety set, the median overall exposure to the study treatment was 364 days in the 300 IR and the placebo groups.Compliance was good throughout the treatment period (>90% per group).
The clinical relevance of the treatment effect of the 300 IR HDM tablet for an EU patient is illustrated in Fig. 1  EAACI-recommended CSMS 0-6 .In calculating the CSMS 0-6 , the RTSS 0-12 component was divided by 4 to give equal importance to the RMS 0-3 .Thus, proportionately, for each of the 4 rhinitis symptoms initially scored from 0 to 3, a change of one severity level corresponded to a score of 0.25 with a maximum score of 0.75.A reduction of À0.32 in the CSMS 0-6 may reflect a decrease in one severity class in 1 symptom, for instance blocked nose, for the whole year, assuming the 3 other symptoms remain stable in severity and the use of rescue medication remains also stable.From the score calculation, it is possible to translate the severity of blocked nose into days with mild, moderate or severe symptom or even days with no symptom over the time period.The example in Fig. 1A considers a patient treated with placebo with an average CSMS 0-6 of 1.52 and suffering from mild blocked nose over 41% of days, moderate blocked nose over 22% of days and severe blocked nose over 15% of days.With a CSMS 0-6 reduction of À0.32, a patient treated with 300 IR HDM tablet scored 1.20 can expect to be free from moderate to severe blocked nose over 1 year.
Alternately, looking at the RMS 0-3 component, it is also possible to translate the medication score into days with use of antihistamines, nasal or oral corticosteroids, assuming the 4 rhinitis symptoms remain stable in severity.The example in Fig. 1B considers a patient treated with placebo (CSMS 0-6 ¼ 1.52) needing oral antihistamines for over 40% of days and nasal corticosteroids for over 7% of days.With a CSMS 0-6 reduction of À0.32, a patient treated with 300 IR HDM tablet (CSMS 0-6 ¼ 1.20) can expect to be free from nasal corticosteroids and to reduce oral antihistamine intake over 1 year.

Other endpoints
During the primary evaluation period, all the clinical endpoints assessed in the EU subpopulation collectively demonstrated the 300 IR HDM tablet was significantly better than placebo (Table 3), supporting the results of the combined symptom and medication scores and their components.In addition, the RCTSS, the TOSS,     3).The 300 IR group and the placebo group differed significantly.With regards to the quality of life, at the end of the treatment period, significant differences were observed in the overall RQLQ score and all the 7 domain scores between the 300 IR and placebo groups (Fig. 3).The point estimate of the overall RQLQ between the 300 IR group and the placebo group at the end of treatment was À0.29 (95%CI [À0.42;À0.15], p < 0.0001) with a relative difference of À17.8%.For the 7 individual domains, the relative differences from placebo ranged from À15.7% for practical problems to À19.1% for nasal symptoms (Fig. 3).

Safety
Overall, the safety profile in the EU subpopulation of this RCT was consistent with that in the overall population, 25 in line with the known safety profile of SLIT.No deaths occurred during the study, and there were no reports of anaphylaxis.No EU participants treated with 300 IR HDM tablet received epinephrine.During the 12month treatment period, 324 (65.1%) patients in the 300 IR group and 254 (51.4%) patients in the placebo group reported at least one treatmentemergent adverse event (TEAE).The most common TEAEs related to the 300 IR HDM tablet were mild or moderate application-site reactions such as oral pruritus, throat irritation, ear pruritus, and mouth edema.One patient experienced a serious TEAE related to the 300 IR HDM tablet.This was an adult who experienced a severe pharyngeal reaction on the second day of treatment immediately after taking the IP at home.He took cetirizine tablets immediately, and the event resolved 1 h later.The patient discontinued the study on the same day.Forty-one patients (8.2%) in the 300 IR group and 2 patients (0.4%) in the placebo group prematurely discontinued the study due to TEAEs suspected to be drug-related, mostly applicationsite reactions.

DISCUSSION
The present study aimed to evaluate post hoc the results of the EU population that participated in the recently published international, randomized, placebo-controlled, phase 3 clinical trial with the 300 IR HDM sublingual tablet, 25 with a focus on 2 balanced symptom and medication scores following recommendations from Health Authorities and international experts, 29,30 the CSMS 0-6 and TCRS 0-24 .
A large patient population of adults and adolescents with HDM-induced AR was recruited in the primary trial and two thirds (n ¼ 818) of the 1262 patients evaluable for efficacy (ie, included in the mFAS) were European.In this subpopulation as Fig. 3 Rhinoconjunctivitis quality of life scores (overall and by domains) at the end of treatment with 300 IR HDM SLIT tablet in the European study population (mFAS).HDM, house dust mite; IR, index of reactivity; mFAS, modified full analysis set; RQLQ, rhinoconjunctivitis quality of life questionnaire; SLIT, sublingual immunotherapy.Statistically significant intergroup differences *p < 0.01, **p 0.0001.in all patients, treatment with the 300 IR HDM tablet was associated with a significant and consistent reduction in the three assessed combined symptom and medication scores (imbalanced and balanced).Absolute and relative differences from placebo were even greater in EU patients with À0.90 and À20.3%, respectively for the average TCS 0-15 , À0.32 and À20.9% for the average CSMS 0-6 , and À1.28 and À21.2% for the average TCRS 0-24 .Noteworthy, this treatment effect is similar or even better than that observed in a RCT in EU patients with HDM-induced AR with another HDM SLIT tablet (12 SQ-HDM, ALK-Abelló, Hørsholm, Denmark) and using a balanced combined score close to the present TCRS 0-24 . 32In that trial, absolute and relative differences in TCRS from placebo were À1.22 and À18%, respectively.For all 3 combined scores, the relative differences between the 300 IR HDM tablet and placebo in this EU subpopulation were greater than the threshold for difference in the primary outcome relative to placebo recommended by the United States Food and Drug Administration (FDA) to achieve clinically meaningful difference (ie, at least À15% with a 95%CI upper limit of at least À10%). 33These differences also exceeded the À20% difference stated by the World Allergy Organization (WAO) 34 and the Global Allergy and Asthma European network (GA2LEN) of the Allergy and its Impact on Asthma (ARIA) initiative. 35However, there is international consensus that a formal validation for the minimal clinically important difference (MCID) of a balanced symptom and medication score as primary endpoint in future trials in AIT is needed for defining the cut-off for a "clinical relevant" treatment effect-size. 29,36From the patient perspective, the results of the EAACIrecommended CSMS 0-6 supported this clinically relevant effect in that they could be translated into a perceivable reduction in symptom severity, for instance blocked nose (reported as the most bothersome), and/or a decrease or cessation of symptom-relieving medication, notably corticosteroids, over a time period.This is a clinically meaningful result obtained already in the first year of treatment of a perennial disease affecting patients continuously exposed to allergens and having difficulty to control the daily symptoms and reduce their need for rescue medication.
The positive results of the other clinical scores assessing the symptoms and medication use in the EU subpopulation like the components of the combined scores, RTSS, RMS, and DMS as well as the RCTSS and the individual nasal or ocular ISSs, collectively strengthen those of the combined scores, supporting the relevance of the 300 IR HDM tablet.In addition, the overall and the seven RQLQ domain scores were significantly lower in the 300 IR group than in the placebo group.Such an improvement in quality of life, which is known to be greatly impaired in patients with HDM-induced AR, contributes to the meaningfulness of this treatment for the patients.
The 300 IR HDM SLIT tablet is currently marketed in Australia, Japan, New Zealand, South Korea, and more recently Europe.In seeking approval in Europe in 2021, the treatment effect of the product was specifically assessed in the EU population that participated in the primary international trial, which was considered pivotal. 25ivotal trials are normally performed in different countries worldwide to cover different healthcare systems, daily practices, and patient populations.It is remarkable that all the endpoint results in the EU subpopulation consistently exceeded those observed in the overall population. 25The lower results in the overall population were essentially driven by differences between active treatment and placebo of lesser extent in other regions and notably in North America.Such a variation between regions may be explained by differences in clinical trial management and/or patients' monitoring.Indeed, it has been acknowledged that in multi-regional clinical trials, treatment effects of drugs may be impacted by varying factors (including recruitment, compliance, subject retention, medical practice, environmental, cultural, socio-economic factors, etc) across regions or subpopulations. 37The EMA ICH guideline E17 on "general principles for planning and design of multi-regional clinical trials" has been recently developed to address these issues but came into effect after the primary international trial was conducted.In addition, differences in patients' clinical characteristics and variations in allergen exposure across regions might have interfered with the trial results. 38A post hoc analysis of the patients' baseline characteristics by region (Supplemental Table 2) revealed that, compared with the EU subpopulation, the North American (NA) was less exposed to HDM, had lower mean levels of HDM-specific IgE, included a higher proportion of polysensitized patients (about two-thirds in North America versus less than 40% in the European Union) with more patients exhibiting confounding sensitizations, therefore more likely to present intercurrent factors that might have affected the efficacy results.In addition, NA participants presented with a longer duration of HDM-AR suggesting they were likely more used to live with their allergy, which could have impacted their way of scoring.Though no notable differences in the combined score results were observed at baseline, the RMS component results were about 2-fold lower in NA versus EU patients and associated with a slightly higher RTSS (Supplemental Table 3).A lower intake of rescue medications in the former might explain the lower decrease in combined score seen in the active group at the end of treatment.Furthermore, the proportion of dropouts was 1.5-1.8-foldhigher within the NA versus the EU subpopulation, the primary reason being due to adverse events (AE) in the active group and withdrawal by the subject in the placebo group (Supplemental Table 2).Assuming that the patients who prematurely withdrew due to AEs (mostly reactions to active treatment) were those who might have benefited most from the active treatment if they have continued, this suggests that remaining NA patients were likely less affected so that the difference in scores versus placebo was less marked.Interestingly, the clinical efficacy of the 300 IR HDM tablet was more pronounced in EU patients with severe enough symptoms to require symptom-relieving medication during the baseline period.This reinforces the value of this treatment during the periods with troublesome symptoms, also allowing the patients to reduce their consumption of rescue medications, particularly nasal corticosteroids.
Finally, as expected, the safety profile of the 300 IR HDM tablet in the EU subpopulation was found as acceptable as in the overall population. 25No severe anaphylactic reactions were reported.
The strengths of this analysis were the large size of the subpopulation studied consisting of about twothirds of the primary trial population and the consistency of results whichever the scores evaluated.
The main limitation was the treatment duration of 12 months.However, the increased effect of this tablet over the 12-month treatment period, as observed in the overall trial population, is important to highlight given that EAACI guidelines recommend a minimum of 3 years of AIT to achieve long-term efficacy. 1ther clinical trials with the 300 IR HDM tablet demonstrated an early onset of efficacy after an interval of only 8-12 weeks, indicating that benefits were apparent also in the first year of treatment. 24,27In addition, one of these trials conducted in Europe showed that efficacy was maintained during a treatment-free follow-up year after 1 year of therapy. 24These findings support the potential of AIT for further improvement beyond 12 months and that continuing AIT will ensure to "consolidate" clinically meaningful benefits which can last after treatment cessation. 39

CONCLUSION
The post hoc data from the international, randomized, placebo-controlled clinical trial focusing on the European HDM-AR adults and adolescents confirm the efficacy and safety of the 300 IR HDM SLIT tablet during the first year of treatment.The results were even better than those observed in the overall population.Moreover, when applying the recommended balanced symptom and medication scores CSMS 0-6 or TCRS 0-24 , a clinically relevant efficacy above the required 20% improvement was shown and translated into clinically meaningful benefits from the patients' perspective.The significant improvement in the overall RQLQ score as well as in all seven domains of the RQLQ unpin the meaningfulness of this treatment for European patients.

Funding
The study as well as the medical writing assistance was sponsored and funded by Stallergenes Greer (Antony, France).

Table 1 .
based on the results of the Relevant baseline characteristics of the European study population (mFAS).Abbreviations: HDM, house dust mite; IgE, immunoglobulin E; IR, index of reactivity; kU/L, kilounits per liter; mFAS, modified full analysis set; N, number of patients in the analysis set; n, number of patients with data; SD, standard deviation.
a After HDM allergens, the next most frequently observed sensitizing allergens (according to a skin prick test) were grass pollen (in 18.2% of the participants) and cat dander (in 16.5%).b Baseline HDM specific serum IgE levels: at least one of both (D. pteronyssinus and/or D. farinae) specific serum IgE value(s) !17.5 kU/L, or both (D. pteronyssinus and D. farinae) specific serum IgE values < 17.5 kU/L In the EU subpopulation, ANCOVA analyses of the average CSMS 0-6 and TCRS 0-24 adding

Table 3 .
Other endpoints during the primary evaluation period in the European study population (mFAS).
Abbreviations: aRCTSS, average rhinoconjunctivitis total symptom score; aTOSS, average total ocular symptom score; HDM, house dust mite; IR, index of reactivity; LS, least squares; mFAS, modified full analysis set; N, number of patients in the analysis set; RQLQ, rhinoconjunctivitis quality of life questionnaire.a LS mean: Back-transformed LS mean obtained from an analysis of covariance of the square root of the average score during the primary evaluation period, except for RQLQ score (no square root).b Point estimate: LS mean difference between 300 IR and placebo.c Relative LS mean difference: [(300 IR LS meanplacebo LS mean)/placebo LS mean] x 100.