**3. Omalizumab in Urticaria**

Omalizumab is a recombinant deoxyribonucleic acid-derived humanized monoclonal antibody manufactured from a mammalian cell line, that selectively binds to IgE. The antibody is an IgG1 kappa that contains human framework regions with the complementary-determining regions of a murine parent antibody that binds to free IgE, preventing its interaction with FcεRI (**Table 1**). It has been firstly indicated for adults and children (6 years of age and above) with moderate to severe persistent allergic asthma. Ten years later, omalizumab has been approved for the treatment of adults and adolescents (12 years of age and above) with CSU refractory to standard of care.

### **3.1 Phase II and III clinical studies**

Omalizumab preliminary dose selection was provided by the phase II study MYSTIQUE, which evaluated the effect of the drug at different dosages [49]. While these results provided the preliminary data, pivotal dose selection was ultimately evaluated in two pivotal phase III efficacy trials (ASTERIA I and ASTERIA II) and was supplemented by data from the safety trial (GLACIAL) [12]. The GLACIAL study was adequately designed and controlled to provide efficacy information as well.

The MYSTIQUE study assessed the efficacy of three doses of omalizumab (75 mg, 300 mg, and 600 mg) as a single subcutaneous injection in patients with CSU refractory to H1-antihistamines (n = 90), which was followed by a 12-week observation period [49]. The primary endpoint was the mean change in UAS7 at Week 4. Patients in the omalizumab 300 mg and 600 mg groups had significantly greater improvements from baseline in the scores of UAS7 and weekly Itch Severity Score (ISS) compared with those in the placebo group. No additional benefits were observed in the 600 mg group over the 300 mg group. UAS7 scores with omalizumab 75 mg showed only marginal differences versus placebo [50]. The most frequently reported (≥5%) treatment-emergent adverse effects (AEs) during the treatment period were upper respiratory tract infection, headache, nasopharyngitis, and dysmenorrhea. Most AEs were mild to moderate in severity and were considered not related to the study drug [49].

In the XCUISITE study, omalizumab was administered according to the dosing table for allergic asthma using baseline IgE level and weight [50]. Treatment effects were analyzed by individual dose levels for the primary endpoint (change from baseline in UAS7 after 24 weeks) [51]. In the groups receiving omalizumab 300 mg and 150 mg every 4 weeks, a considerable improvement was observed in the UAS7 score compared with that in the placebo group, with a more pronounced effect observed with 300 mg [12]. Although the results of the study suggested a dose– response relationship, no conclusions were made regarding the comparative efficacy between the dose levels since the number of patients in each group was small (n = 6–7) and participants were not randomly assigned to the different dose levels [52]. In terms of safety in the XCUISITE study, the overall incidence of AEs during the treatment period was similar between the omalizumab and placebo groups. The


**63**

 *Urticaria.*

**Table**

**1.**

 *Summary of the Anti-IgE Antibodies in Chronic*

most frequent AEs (>5%) in both groups were diarrhea, nasopharyngitis, and headache. No severe AEs or deaths related to omalizumab were reported [51].

The ASTERIA I, ASTERIA II, and GLACIAL studies were part of the omalizumab registration program in CSU. These were phase III, randomized, multicenter, double-blind, placebo-controlled studies that evaluated the efficacy and safety of omalizumab in patients with CSU [52–54]. Patients with CSU who remained symptomatic despite H1-antihistamine therapy were randomized to receive either placebo or subcutis omalizumab at the dosage of 75 mg, 150 mg, or 300 mg every 4 weeks for a total of 24 weeks in ASTERIA I (n = 319) and 12 weeks in ASTERIA II (n = 323) [52, 53]. The primary endpoint in both trials was the mean change in the ISS score at Week 12. Secondary was to evaluate the variation from baseline to Week 12 in the UAS7 score, weekly number of hives score, median time to minimally important difference in the ISS, weekly size of the largest hive score, proportion of patients with UAS7 ≤ 6, change in the Dermatology Life Quality Index score, proportion of patients with UAS7 = 0, and proportion of angioedemafree days from Week 4 to Week 12.

Instead, GLACIAL (n = 336) primarily evaluated the safety of omalizumab in patients with CSU who remained symptomatic despite treatment with H1-antihistamines (at up to four times the approved dose) plus H2-antihistamines and/or leukotriene receptor antagonists [51], according to the EAACI/GA<sup>2</sup> LEN/EDF/WAO urticaria guideline at that time [1]. In this study, patients were randomized 3:1 to receive either subcutaneous omalizumab 300 mg every 4 weeks or placebo for 24 weeks.

In all three studies, the treatment period was followed by a 16-week observation period during which no treatment was given [52]. Overall, no new safety issues were identified in the CSU clinical program [51]. No deaths occurred during either trial. The pivotal efficacy trials demonstrated a consistent dose-dependent treatment effect for the evaluated endpoints [49].

Anyway the licensed dosage for omalizumab for refractory CSU, with or without angioedema, in Europe is 300 mg every 4 weeks, independent of patient body weight, body mass index or serum IgE level, while in the USA this is either 150 or 300 mg [12, 52]. Instead, only the dosage of 300 mg every 4 weeks has been proven to be effective in case of angioedema. Currently, the licensed dosage in Italy is 300 mg every 4 weeks over a 6-month period, and in the case of disease recurrence, a minimum of 8 weeks suspension from omalizumab is mandatory, and then it can be prescribed again for a further 5 months only [12]. This schedule (6 months treatment, 8 weeks suspension, and 5 months therapy) can be repeated for eventual relapses; however, this de novo treatment is considered off-label.

To date, there are no licensed treatment options for CIndU and the recommended dosage with omalizumab is similar to CSU.

#### **3.2 Omalizumab: real-life evidences**

In clinical settings, the treatment of refractory CSU with omalizumab has been shown to be similar to, or in some cases even better than, those reported by the pivotal randomized controlled trials [12, 55–61].

The retrospective analysis of the three pivotal studies (ASTERIA I, ASTERIA II, and GLACIAL) put first in evidence that some CSU patients respond to treatment more quickly than others and for this reason two different categories were identified: "fast responders" for those who respond within 4–6 weeks and "slow responders" for whom obtain a response more gradually (from 12 to 16 weeks) [12]. However, "slow responders" may still respond even after 24 weeks, while some "fast responders" may obtain a response to treatment within 1 week, suggesting that

the response patterns of patients to omalizumab may be due to the different pathomechanisms of the disease. These two different patterns of response have been soon confirmed by real-life experiences [12, 61–63]. In addition, the clinical assessment of CSU activity was not always uniform in all studies and different patient-reported outcome measures are used, either alone or in combination, to assess disease activity and guide the assessment of treatment efficacy.

Real-world studies have shown a response to treatment in 48–80% cases, while 7–14% are non-responders and 8–50% relapse after drug discontinuation [12, 55–61], supporting the efficacy and safety of omalizumab in CSU patients with an inadequate response to H1-antihistamines. These studies add precious information for the clinical management of CSU, but often present a relatively small sample size population and sometimes include different doses and administration timing of omalizumab. In particular, real-world studies demonstrated that omalizumab administration reduces the use of other CIndU/CSU-related medications. A recent large real-world retrospective study including 1546 patients with CIndU/CSU treated with omalizumab revealed that the majority started with a dosage of 300 mg and received the drug for an average of 9 months without dosing titration up or down [64]. Moreover, the use of other medications, such as corticosteroids and antidepressants, was consistently decreasing during the follow-up period, from 72.8% over the first 3 months to 58.5% over the last 3 months.

Additionally, real-life experiences have confirmed that there are different patient profiles according to omalizumab response [63, 65, 66]:


Other different strategies mainly involve either modification of the omalizumab dose or a change in the treatment interval. Dose increases or reductions, if the complete CU symptoms control is achieved, should be stepwise [63].

Data on the response rate to omalizumab is available from meta-analyses and real-world evidence, but not all of them have assessed the time to response and, due to the different dosages and treatment durations, it is difficult to draw a common conclusion from these studies [32, 46, 49, 50, 53, 56, 57, 66–74]. Consequently, several parameters have been suggested to potentially predict treatment response, or possible treatment relapse. Some studies have been focused on different baseline clinical and laboratory parameters in order to identify the predictors of response to omalizumab in CSU patients. Asero et al. found that high levels of D-dimer seems to be a marker of response to treatment [32], but more recently the same authors and other studies indicate D-dimer only as a activity/severity marker in CSU patients and its plasma levels are reduced by omalizumab both in patients with and without angioedema at baseline [75]. Instead, many studies have shown that total IgE levels can be a marker of response to omalizumab [76]. Marzano et al. recently confirmed IgE basal levels as a reliable biomarker predicting response to treatment in CSU patients, while they did not support the usefulness of D-dimer [62]. In a singlecenter study on 47 CSU patients the baseline basophil FcεRI expression was found to be a potential immunological predictor of good and fast response to omalizumab (100% sensitivity and 73.2% specificity) [34].

The analysis of omalizumab responders in a prospective study of 64 patients showed that most basophil histamine release assay (BHRA)-positive patients

responded only after the second injection, with a median time to response of 29 days, whereas BHRA-negative patients had a median time to response of only 2 days [77].

In a retrospective study of 41 antihistamine-refractory CU patients, the lack of basophil CD203c-upregulating activity in their serum correlated negatively with a clinical respond to omalizumab [78]. In detail, a significant association was found between the response and CD203c-upregulating activity, autoimmune phenotype, low IgE levels, and high eosinophil count levels.

Greater number of prior medications was associated with a lack of response to omalizumab in a study of 52 patients with severe CU, whereas the presence of anaphylaxis, angioedema, dermatographism, steroid use, and disease duration were not [79].

Furthermore, CSU duration before omalizumab and baseline UAS7 may be considered a negative markers of response and high relapse risk [62]. Although the response to omalizumab should not be dose dependent in CSU, real-life settings have shown that body mass index could influence the performance of the drug [17].

In a cohort of 154 patients the following factors were described as possible predictors of a favourable response to omalizumab [80]:


Over 85% of patients who present these characteristics achieved a complete respond to treatment.

In relation to the dosing, the proportion of patients who showed complete response to omalizumab 150 mg ranged from 15–22% in clinical trials and from 36– 79% in real-world studies. Regarding omalizumab 300 mg, the proportion of complete responders ranged from 34–44% in clinical trials and from 40% to 84.6% in real-life settings. However, not all real-world studies provided information on treatment duration. In few real-world studies where patients have received either/ both omalizumab 150 mg and 300 mg, the complete response was observed in 47– 83%. In addition, a complete response was achieved as early as the day after the administration of the first dose or within 5 months [66–74].

Real-world settings support that repeated treatment cycles should be required in several CSU patients [12, 70, 74, 81, 82]. Regarding the retreatment, omalizumab seems to be highly efficient in relapsed patients who previously had responded well [74]. An Italian retrospective clinical analysis revealed that the second cycle treatment with omalizumab is effective more quickly compared to the first cycle response [12]. Based on current international guidelines, omalizumab labelling information and experience in clinical practice, an Italian group provided treatment recommendations regarding the use of omalizumab in patients with CSU concluding that repeated cycles or extended treatment may be necessary in patients with disease relapse or late treatment response [81]. These authors suggested to continue the treatment when patients have a UAS7 > 6 and/or UCT < 12.

Among responders, after discontinuation of omalizumab the treatment can be resumed at a later stage with the same degree of symptom control [82].

All the real-world studies underlined the high safety prophile of omalizumab also in continuous and long-term administration. Finally, in a meta-analysis of 67 published reports, benefits and safety of omalizumab in the real-world treatment of CSU have met or exceeded results achieved in clinical trials [83].

#### **3.3 Omalizumab performances optimization in clinical practice**

Current evidence indicates that CSU usually last from 3 to 12 months, but patients may be affected for more than 1 year (sometimes even more than 5 years) [84]. However, recommendations regarding treatment duration and re-treatment after symptoms return are lacking. Nevertheless, the primary results of the OPTIMA study have shown that approximately 88% of patients who relapsed after being previously well-controlled with omalizumab, regain symptom control upon re-treatment within 3 months [85]. Similarly, phase IV XTEND-CIU study and few real-world studies have shown re-treatment to be effective in CSU patients who had previously responded to omalizumab but who relapsed after treatment withdrawal [4, 86]. To date, there are limited data comparing the therapeutic effect of omalizumab for patients with CSU, CIndU, and CSU plus CIndU. A recent chinese study revealed that omalizumab is highly effective and safe in 138 patients with difficult-to-treat CSU, CIndU, or both [87]. Among the CU patients enrolled, 87% responded to omalizumab therapy and those with higher baseline total IgE levels and longer disease durations showed more likely to experience rapid relapse after discontinuation of the drug.

Many other important questions regarding the use of omalizumab remain to be answered in order to optimize treatment management and patient outcomes. In particular, further investigations regarding predictors of good outcome, optimal dose, and dosing intervals based on treatment response to omalizumab in CSU are needed. A personalized therapeutic algorithm according to the patient clinical and bio-markers, modulated on the dose–response pattern, should facilitate the clinical management of omalizumab and help clinicians to determine the most appropriate therapeutic strategy for CSU. Future research is, therefore, required to evaluate the role of omalizumab in the various subtypes of CU as well as to establish standardized protocols for dosing and monitoring adverse effects of long-term therapy.

### **4. Ligelizumab (QGE031)**

Even though omalizumab has been changing the management of CU, there is still a need for new targets and new biologics targeting new pathways in the management of the disease, which should provide long-lasting remission, be administered orally and cheaper. Among the CSU treatments that are still under clinical trials, there is anothers anti-IgE drug called ligelizumab (QGE031), which has been developed with the intention of overcoming some of the limitations associated with omalizumab [88].

### **4.1 Ligelizumab: what is it and how does it work in Chronic Spontaneous Urticaria**

Ligelizumab, a next-generation high-affinity fully human monoclonal IgG anti-IgE antibody, demonstrated dose- and time-dependent suppression of free IgE, basophil FcεRI and basophil surface IgE superior in extent (free IgE and surface

IgE) and duration to omalizumab (**Table 1**) [89, 90]. Ligelizumab recognizes a distinct IgE epitope only partially overlapping with that of omalizumab, interacting across the IgE-Fc dimer and favors the recognition of IgE in an open conformation different from its FcεRI- or CD23-bound conformations. Moreover, it binds IgE with significantly higher affinity (almost 50-fold higher) than omalizumab and shows a correspondingly enhanced inhibition of IgE binding to FcεRI and basophil activation. However, ligelizumab is inferior to omalizumab in preventing IgE binding to CD23. Structural analysis indicates that differences in the ligelizumab epitope and spatial orientation on IgE contribute to this differential inhibition [91].

Indeed, ligelizumab and omalizumab recognize distinct binding epitopes in the IgE Cε3 domain, showing some overlap but also different sensitivities to IgE conformation. On one side, the increased affinity of ligelizumab for IgE is superior than omalizumab regarding neutralization of free serum IgE, on the other side the additional mode of action for ligelizumab through the inhibition of IgE production may provide additional therapeutic benefit. Indeed, ligelizumab is more efficient in suppressing FcεRI-dependent allergic reactions in an in vivo model, while omalizumab may have advantages in blocking antigen presentation and transport processes that are dependent on IgE:CD23 interactions [92, 93].

#### **4.2 Ligelizumab clinical studies**

Currently, ligelizumab is being developed solely for the treatment of CSU. Phase IIb randomized controlled trial (NCT02477332) in CSU (CQGE031C2201) results demonstrated ligelizumab to be efficacious at 72 mg and 240 mg dosage, showing superiority over omalizumab and a comparable good safety profile [94]. The subsequent extension study (NCT02649218) in CSU (CQGE031C2201E1) proved the efficacy and safety of the ligelizumab at the dose of 240 mg every 4 weeks for a 1 year period, achiving more prolonged symptom control compared to the core study [95, 96].

#### *4.2.1 CQGE031C2201*

This was a 20-weeks multi-center, randomized, double-blind, placebo- and active controlled phase IIb dose-range finding study in subjects with CSU inadequately controlled [94]. CSU patients included in the study had to have a moderateto-severe CSU defined as UAS7 of at least 16, 7 days hives severity score (HSS7) of at least 8, and in-clinic UAS of at least 4 (range 1 to 6) on at least one of the screening visit days. Exclusion criteria were represented by a previous exposure to omalizumab or ligelizumab, any other skin disease that is associated with chronic itching that might confound the trial evaluations and results, and a clearly defined underlying cause of CU other than CSU (e.g., inducible urticaria).

Subjects were randomized into 1 of 6 parallel treatment arms at a ratio of 1:2:2:2:1:1 (subcutaneous injections every 4 weeks of ligelizumab 24 mg, 72 mg, or 240 mg, omalizumab at a dose of 300 mg, a single dose of ligelizumab 120 mg followed by placebo or placebo) for the 20-week treatment period. The single 120 mg dose of ligelizumab was used to gain blinded wash-out information in relation to return of symptoms.

During the screening, treatment, and follow-up periods, nonsedating H1-antihistamines were used as rescue medication. Moreover, as background medication, this trial required concurrent use of H1-antihistamines at locally approved doses or at increased doses up to four times alone or in combination with H2-antihistamines or leukotriene-receptor antagonists (montelukast, zafirlukast, or pranlukast), according to the EAACI/GA<sup>2</sup> LEN/EDF/WAO urticaria guideline at that time [1].

Primary end-point was the achievement of complete hives response (HSS7 = 0) at week 12 (four weeks after the last injection), similar to phase III trials of omalizumab. Among 574 patients screened, 382 were included and 338 completed the treatment phase. The mean age SD of the study population was 43.3 12.5 years (range 18 to 75 years) and 75% of subjects were female. Mean time since diagnosis of CSU was 4.3 6.0 years. Median IgE levels at baseline was 87.2 IU/ml (range 0 to 14100).

With ligelizumab the main objective of the trial was achieved, showing a dose– response relationship with respect to the achievement of a HSS7 of 0 at week 12. The relationship resulted in a plateau starting close to the 72 mg dose of ligelizumab, while no further improvement in response was noted with the dosage of 240 mg.

At week 12, complete hive response was achieved in 30%, 51%, and 42% of patients treated with 24 mg, 72 mg, and 240 mg ligelizumab, respectively. Instead, a HSS7 of 0 was achieved only in 26% of patients with omalizumab and in none of those in the placebo group. The 7 days itch severity score (ISS7) showed a pattern similar to that seen with the hives-severity score. At week 12, UAS7 of 0 was achieved in 30%, 44%, and 40% of patients treated with ligelizumab 24 mg, 72 mg, and 240 mg, respectively, in comparison to 26% with omalizumab and none with placebo. Considering the scores (ISS7, UAS7, and HSS7) achieved, ligelizumab demonstrated superiority not only over placebo but also over omalizumab. In addition to hives and itch the AAS decreased to 21.1, 37.6, and 27.3 among patients treated with 24 mg, 72 mg, and 240 mg ligelizumab, respectively, in comparison to 23.1 in patients with omalizumab and 23.6 in the placebo group.

At week 4, the effect of the single 120 mg ligelizumab dose was similar to that seen with 72 mg and 240 mg and lasted until week 8. In contrast, a partial relapse of symptoms was noted with the 72 mg ligelizumab toward the end of the administration interval of four weeks. These data gave evidence that a dose higher than 72 mg ligelizumab could potentially provide enough drug effect throughout the administration interval of four weeks, minimizing symptom relapse. In support of this sustained treatment effect, the median time to loss of complete response in patients who had an UAS7 of 0 at the end of the treatment (week 20) was greatest in the patients treated with 240 mg of ligelizumab (10.5 weeks), while was similar in the groups that received 72 mg of ligelizumab or 300 mg of omalizumab (4 weeks).

Similar to omalizumab, the most frequent AEs were mild to moderate injection site reactions after subcutaneous administration (4% and 7% of patients treated with the 72 mg and 240 mg, respectively). All other minor AEs (mainly upper respiratory infections and headaches) showed no meaningful difference among the trial groups. Deaths, anaphylaxis or serious adverse events to ligelizumab have not been reported.

### *4.2.2 CQGE031C2201E1*

Patients who completed CQGE031C2201 were eligible to be enrolled in this extension study at week 32 that confirmed the safety of the long-term (52 weeks) administration of the highest dose of ligelizumab (subcutaneous injections every 4 weeks of ligelizumab 240 mg) [95]. At week 52, 61.1% of patients achieved UAS7 ≤ 6 and, after stopping treatment, the median time of well-controlled disease was 28.0 weeks. These results implicate a longer treatment effect of ligelizumab compared to omalizumab [96].

#### *4.2.3 CQGE031C1301*

CQGE031C1301 represents a phase II multi-center, open-label study (NCT03907878) to investigate the safety/tolerability and efficacy of ligelizumab 120 mg every 4 weeks in adult Japanese patients with CSU inadequately controlled with H1-antihistamines. Currently, CQGE031C1301 is still ongoing.
