Diffusion Characteristics of LetibotulinumtoxinA, OnabotulinumtoxinA, and AbobotulinumtoxinA and its Impact on Muscle Relaxation: A Randomized Split-Face Clinical Trial

Abstract

Introduction

Injections with botulinumtoxinA (BoNTA) are the most common nonsurgical aesthetic procedure but carry risks such as unintended muscle diffusion. Understanding formulation behavior is key to optimizing safety and efficacy.

This study compares the diffusion characteristics from letibotulinumtoxinA (Leti-BoNTA) to onabotulinumtoxinA (Ona-BoNTA) and abobotulinumtoxinA (Abo-BoNTA) and its impact on muscle relaxation of frontalis muscle.

Methods

In a double-blind, randomized trial, 30 healthy adults received Leti-BoNTA on one forehead side and either Ona-BoNTA or Abo-BoNTA on the other. Anhidrosis was measured via Minor’s starch test over 6 months, and wrinkle severity was assessed using standardized photography and the Croma Scale.

Results

Leti-BoNTA had a significantly smaller maximal anhidrotic area than Ona-BoNTA (−15.1 ± 5.5 cm², p < 0.001) and Abo-BoNTA (-25.2 ± 14.5 cm², p < 0.001). An area under the curve (AUC) analysis confirmed the largest area of anhidrosis for Abo-BONTA over the 6-month period, followed by Ona-BONTA and Leti-BoNTA. Despite its lower diffusion, Leti-BoNTA effectively improved wrinkles, with ≥ 1-point improvement in 92% of subjects by week 2.

Conclusions

Leti-BoNTA provides wrinkle reduction with a more limited diffusion, as assessed with the Minor’s starch–iodine test. Its precise action in this trial implies to be a viable option when controlled spread is essential.

Clinical Trial Registration

The trial EU CT: 2024–511047-26–01 was registered on 23 March 2024.

Key Summary Points

Why carry out this study?

BotulinumtoxinA (BoNTA) formulations differ in their diffusion profiles, which can influence clinical outcomes; however, comparative data—especially for letibotulinumtoxinA (Leti-BoNTA)—are limited.

This study aims to assess and compare the diffusion and efficacy characteristics of Leti-BoNTA versus onabotulinumtoxinA (Ona-BoNTA) and abobotulinumtoxinA (Abo-BoNTA) in a split-face clinical trial.

What was learned from the study?

Leti-BoNTA demonstrated comparable muscle relaxation effects and predictable diffusion properties relative to Ona-BoNTA and Abo-BoNTA.

These findings support Leti-BoNTA as a clinically equivalent alternative to other BoNTA formulations, potentially expanding therapeutic and cost-effective options in aesthetic treatment.

Introduction

The field of aesthetic medicine has gained increasing influence in recent years [1, 2]. According to the International Society of Aesthetic Plastic Surgery, injections with botulinumtoxinA (BoNTA) are not only the most frequently performed nonsurgical procedure across all age groups but also the most widely used aesthetic intervention overall [3]. However, with the growing interest in neuromodulator injections, the risk of potential muscle-related side effects also increases—including unintended muscle weakness, asymmetry, or ptosis if the toxin spreads beyond the target area [4]. To minimize these risks, understanding the diffusion and distribution of different formulations is crucial, which can be assessed through methods such as the iodine−starch test and standardized forehead line assessments.

The divergence of botulinum toxin products, along with their unique clinical characteristics and criteria such as safety, onset, and duration, plays a crucial role in their differentiation. For many years, diffusion has been considered a defining factor that distinguishes one toxin from another. However, there is ongoing debate about the terminology used to describe this phenomenon. The term “diffusion” is often used; however, some literature suggests that “migration” may be a more precise term. Pickett et al. (2008) highlighted that comparing different BoNTA formulations presents methodological challenges, as observed differences in distribution may be influenced by factors such as dosing variations and injection techniques. Regardless of the terminology used, these processes should be both limited and predictable in aesthetic applications. While a confined diffusion pattern is often desired to ensure localized clinical effects and minimize unintended side effects, such as eyelid ptosis or brow asymmetry, some degree of diffusion may be clinically beneficial—particularly in broader anatomical areas such as the forehead or platysma, where wider muscular coverage is required for optimal outcomes. Therefore, achieving a balance between precision and sufficient therapeutic spread is essential for predictable and effective aesthetic improvements [5].

In addition, procedural variables such as dose, dilution volume, and injection technique are known to significantly affect the diffusion behavior of BoNTA [5]. These multifactorial influences underscore the need for cautious interpretation of diffusion-related outcomes in aesthetic BoNTA research, particularly when comparing different formulations. Clinical decisions should therefore be guided by both the pharmacological profile of the product and the specific treatment context.

Currently, several BoNTA formulations are approved for aesthetic use, including letibotulinumtoxinA (Leti-BoNTA; Croma-Pharma GmbH, Leobendorf, Austria [Letybo^®]), onabotulinumtoxinA (Ona-BoNTA; Allergan Inc., Irvine, CA, USA [Botox^®]), and abobotulinumtoxinA (Abo-BoNTA; Ipsen Ltd., Berkshire, UK [Dysport^®]). All three products are synthesized from the same strain of the anaerobic bacterium Clostridium botulinum. In aesthetic applications, precise localization of the effect is crucial, as facial injection sites are close to nontarget muscles. Understanding the diffusion of different BoNTA formulations is therefore essential to optimize treatment selection and injection techniques.

Leti-BoNTA is a 900 kilodalton (kDa) BoNTA, derived from Clostridium botulinum strain CBFC26, designed for both aesthetic and therapeutic applications. It has been rigorously evaluated in phase 3 clinical trials, demonstrating high efficacy and precision and a favorable safety profile in the treatment of moderate–to–severe glabellar lines [6]. Furthermore, Leti-BoNTA was demonstrated to be noninferior versus Ona-BoNTA in the treatment of glabellar lines and crow’s feet [6].

Upon injection, BoNTA inhibits the release of acetylcholine not only at sympathetic nerve terminals, thereby preventing muscle contraction, but also at exocrine glands, leading to a temporary cessation of sweating. As suggested by several studies, the resulting anhidrotic area can serve as an indicator of the spread of the BoNTA formulation used. It is hypothesized that a larger diffusion area corresponds to a wider toxin spread, which may in turn lead to a broader clinical effect, including greater muscle relaxation. This principle has been applied in the present study, which aims to evaluate the diffusion characteristics of Leti-BoNTA in comparison with Ona-BoNTA and Abo-BoNTA by assessing their anhidrotic effects. Nevertheless, injections were not performed to focus on muscle relaxation but to provide deeper knowledge about diffusion characteristics.

To date, however, no data are available on the diffusion properties of Leti-BoNTA in relation to clinical efficacy. Such data could be valuable in refining clinical protocols, adjusting injection points, and optimizing dosage regimens to enhance both efficacy and safety.

Materials and Methods

This was a double-blind, randomized, single-dose, single center study that enrolled healthy patients at the University of Hamburg. The study (EU clinical trial (CT): 2024–511047-26-01) was conducted in accordance with the Declaration of Helsinki and Good Clinical Practice (GCP) guidelines. The research protocol was reviewed and approved by the Ethics Committee of the Medical Association of Munich (Ethikkommission bei der Medizinischen Fakultät der Ludwig-Maximilians-Universität München, Pettenkoferstraße 8, München). All participants provided written informed consent to participate in the study. Consent for publication was obtained from all participants for whom identifiable data are included. All participants provided written informed consent for publication.

Eligible study participants were healthy male and female subjects aged 18–75 with a body mass index (BMI) of 16–27 kg/m² and a healthy skin test area with uniform sweating activity and no areas of anhidrosis under standardized sweating conditions, assessed during the screening period (day −14 to day −1). The main inclusion and exclusion criteria are listed in Table 1.

Table 1.

Eligibility criteria for participation in the study

Inclusion criteria
Fitzpatrick skin type (FST) I–VI
18–75-year-old prerequisites
Moderate–to–heavy wrinkling (in motion)
Uniform sweating activity and no areas of anhidrosis under standardized conditions
Unchanged skin care routine for at least 3 months
Healthy skin and a stable state of health

Exclusion criteria
BMI < 16 or ≥ 27 kg/m2
Asymmetrical forehead wrinkles
Active skin lesions/infections or irritations in the treatment area
Previous treatment (upper third of the face) with fillers of any kind within 12 months before the start of the study/permanent fillers
Pregnancy/breastfeeding
Previous treatment of the forehead within 6 months prior to the beginning of the study (upper third of the face) with botulinum toxin of any serotype prior to baseline
Known hypersensitivity to the investigational product or its excipient substances
Any medical condition that may pose an increased risk to the subject due to botulinum toxin, including diagnosed myasthenia gravis, Eaton–Lambert syndrome, amyotrophic lateral sclerosis, marked atrophy or weakness of the target muscles, or any other condition that may impair neuromuscular function or contraindicate botulinum toxin therapy
Inability to significantly reduce tension lines on the forehead, even if they are physically pulled apart
Planned use of a muscle relaxant within 2 weeks prior to or during the study
Pronounced asymmetry of the face or ptosis of the eyelids and of the eyebrows or current paralysis or neuromuscular connection disorders as assessed by the investigator
Use of prohibited drugs, including anticholinergics or drugs that could impair neuromuscular function, including aminoglycoside antibiotics and curare-like compounds
Use of concomitant medication: lincosamides (lincomycin, clindamycin, or pirlimycin), polymyxins (polymyxin B and E, the latter also known as colistin), spectinomycin, (aminocyclitol), and cholinesterase inhibitors rivastigmine, donepezil, galantamine, pyridostigmine, or neostigmine
Previous autoimmune disease and immunosuppressants, allergies to the botulinum toxins and its experts, previous trauma (< 6 months) in the previous 3 months, or muscular diseases diagnosed

After receiving written informed consent, eligible patients were randomized to receive two of the three study medications on contralateral sides of the forehead. The choice of the dosage of the investigational product was based on national guidelines and the dosage recommended by the manufacturer [7]. Each subject was randomly assigned to receive Leti-BoNTA on one side of the forehead and Ona-BoNTA or Abo-BoNTA on the other side of the forehead. An overview of the specific characteristics of each botulinum toxin formulation, including excipients and the producing cell line, is provided in Table 2.

Table 2.

Pharmaceutical characteristics of BoNTA formulations

BoNTA formulation	Serotype	Fermentation (strain C. botulinum)	MW of purified product	Excipients per 100-unit vial	Stabilization method
LetibotulinumtoxinA	BotulinumtoxinA	CBFC26-strainA [8]	900 kDa [9]	HSA: 0.5 mg NaCl: 0.9 mg [9]	Freeze-drying [9]
OnabotulinumtoxinA	BotulinumtoxinA	Hall (Allergan strain) [10]	~900 kDa [10]	HSA: 0.5 mg NaCl: 0.9 mg [10]	Vacuum-dried [10]
AbobotulinumtoxinA	BotulinumtoxinA	Hall strain [10]	300–500 kDa [11]	HSA: 0.125 mg Lactose: 2.5 mg/500U [11]	Freeze-drying [11]

HSA human serum albumin, MW molecular weight

Each of the two selected products was injected on one side of the forehead with two injection points placed on each side. For each BoNTA preparation, the total injection volume of 0.2 mL was identical. In respect to the line of convergence (C-line), a template was used to ensure that the injection points were comparable (Fig. 1).

Fig. 1.

Treatment injection template; adjusted from [17]

To ensure blinding, all syringes were prepared by an independent third party using identical labeling and standardized volumes, thereby masking any visual or tactile differences between products. Both the injector and participants were blinded to treatment allocation to minimize observer and subject bias.

As Leti-BoNTA and Ona-BoNTA are equipotent, a total dose of 4 U each was used. For Abo-BoNTA, a total of 10 U was used, on the basis of a dose conversion ratio of 1:2.5 onabotulinumtoxinA: abobotulinumtoxinA, as recommended in randomized controlled trials and in reviews, as well as the manufacturer’s recommendations and the official labeling of the product [12–14]. Each BoNTA formulation was reconstituted according to the package leaflet, as detailed in Table 3.

Table 3.

Reconstitution of injected BoNTA formulations

BoNTA formulation	Brand name	Total dose	Dilution
LetibotulinumtoxinA	Letybo	4 U	50 U in vial diluted in 1.25 mL of 0.9% unpreserved NaCl
OnabotulinumtoxinA	Botox	4 U	50 U in vial diluted in 1.25 mL of 0.9% unpreserved NaCl
AbobotulinumtoxinA	Dysport	10 U	500 U in vial diluted in 5.0 mL of 0.9% unpreserved NaCl

On day 1, the intramuscular injections were applied perpendicular to the skin surface with a 30-G needle on the midpupillary line 3 cm above the orbital rim (Fig. 1). The area of anhidrosis was assessed using the starch test, according to Minor et al. [15]. Patients were instructed not to wear makeup or any dermatological products on the morning of the test. The test was conducted as follows: briefly, the skin was cleaned with 0.9% NaCl and dried thereafter [16]. A 2% iodine solution was then applied using a swab stick and allowed to dry. Following starch application, sweating was provoked on a mechanical treadmill. Optimal development of the dark blue coloration was awaited, prior to documentation of the anhidrotic halos using standardized digital photography (VisioFace^® 1000D, Courage + Khazaka electronic GmbH, Cologne, Germany). Factors such as camera angle and parallax, lighting conditions, and the absence of calibration markers or pixel-density control were taken into account, as they may contribute to some variability in the measurements.

The area of anhidrosis was measured using a standardized program. The starch was removed using an alcohol swab. Spread was evaluated by analysis of the area of anhidrosis of each product. The Minor’s starch test was carried out on days 4, 8, 15, 22, 29, 43, 57, 85, 113, 141, and 169.

All statistical analysis were conducted using IBM^® SPSS^® Version 28 (IBM Corporation, Armonk, New York, USA). The study lasted a period of 6 months (169 days).

The primary outcome parameter was the maximum area of anhidrosis within 6 weeks (43 days). The secondary parameter was the area under the curve (AUC) for anhidrosis over a period of 6 months and a live rating of the forehead lines (FHL) at rest and in movement. The AUC, commonly used in clinical pharmacology to quantify overall drug exposure and compare different drugs, facilitated the comparison of the area of anhidrosis for the three BoNTA preparations over time.

Safety analyses included monitoring adverse events, vital signs, physical examinations, and concomitant medications.

The primary outcome parameter, the maximal area of anhidrosis within 6 weeks (43 days), was evaluated using two paired sample t-tests in the two split-face subsets. These tests compare Leti-BoNTA with Ona-BoNTA and Leti-BoNTA with Abo-BoNTA. To correct for multiple testing, α = 0.025 was used instead of α = 0.05. The secondary outcome, AUC for 6 months, was also assessed using two paired sample t-tests.

As a further exploratory analysis, the interaction of time and treatment was tested in a linear mixed model with the fixed effects: treatment, time, and the interaction of time and treatment.

Both primary and secondary analyses were based on the per-protocol set (PPS). Sensitivity analyses were performed using the full analysis set (FAS), and descriptive summary statistics were calculated for all outcome parameters.

Results

Disposition of Subject

Of the 35 screened subjects, 30 met the eligibility criteria on day 1 and were subsequently enrolled, as per the planned sample size of 30.

All 30 subjects were randomized and treated with study medication. As four subjects were lost to follow-up, 26 subjects belong to the safety evaluation set (SES) and the FAS. Patients in the FAS had a mean age of 35.2 years, a mean weight of 68.5 kg, and a mean BMI of 24.2 kg/m². The subjects who completed the full 6-month study period were evenly allocated into two groups: 13 participants received a combination of Leti-BoNTA and Ona-BoNTA (Group A), while the remaining 13 received a combination of Leti-BoNTA and Abo-BoNTA (Group B) to compare the toxin intraindividually.

Primary Outcome Parameter Result

All patients responded to the BoNTA injection and showed a positive reaction to the Minor’s test over time. (Fig. 2).

Fig. 2.

Visible anhidrotic halos from three different subjects on day 43; a injected with letibotulinumtoxinA on the right and abobotulinumtoxinA on the left; b injected with letibotulinumtoxinA on the left and onabotulinumtoxinA on the right; c injected with letibotulinumtoxinA on the left and abobotulinumtoxinA on the right

The primary outcome parameter was the maximal area of anhidrosis within 6 weeks (Fig. 3). The mean maximal areas of anhidrosis for group A were 30.7 ± 15.0 cm² (Leti-BoNTA) and 45.8 ± 14.7 cm² (Ona-BoNTA) (n = 13); for group B they were 36.2 ± 11.4 cm² (Leti-BoNTA) and 61.47 ± 12.9 cm² (Abo-BoNTA) (n = 13).

Fig. 3.

The maximal area of anhidrosis of letibotulinumtoxinA, onabotulinumtoxinA, and abobotulinumtoxinA within 6 weeks

The mean difference in maximal area of anhidrosis from Leti-BoNTA to Ona-BoNTA was −15.1 ± 5.5 cm² (95% confidence intervals [CI]: −18.5, −11.8) and was significantly smaller (p < 0.001) than that of Ona-BoNTA.

The mean difference in maximal area of anhidrosis from Leti-BoNTA to Abo-BoNTA was −25.2 ± 14.5 cm² (95% CI: −34.0, −16.5) and was significantly smaller (p < 0.001) than that of Abo-BoNTA.

Secondary Outcome Parameter Result

The secondary outcome parameter was the AUC of anhidrosis for Leti-BoNTA, Ona-BoNTA, and Abo-BoNTA over 6 months (Fig. 4). The difference between the mean AUC of Leti-BoNTA and that of Ona-BoNTA and Abo-BoNTA was calculated. Over 6 months, the mean difference in AUC from Leti-BoNTA was −2056.7 d cm² (95% CI: −2531.9, −1581.5) for Ona-BoNTA and −3172.6 d cm² (95% CI: −4082.0, −2263.2) for Abo-BoNTA.

Fig. 4.

AUC for anhidrosis for letibotulinumtoxinA, onabotulinumtoxinA, and abobotulinumtoxinA over 6 months

The area of anhidrosis for Leti-BoNTA was significantly smaller than that of Ona-BoNTA (p < 0.001) and also smaller than that of Abo-BoNTA (p < 0.001) over 6 months.

A linear mixed model was used to examine the effects of treatment, time, and their interaction on diffusion characteristics. Both treatment and time had statistically significant main effects (p < 0.001), indicating a meaningful relationship between these variables. In addition, a significant linear decline was observed across the overall sample (regression coefficient [RC]: −2.715; p < 0.001), suggesting that diffusion characteristics decreased over time.

Another secondary outcome parameter was the assessment of wrinkle severity as a key parameter in evaluating treatment efficacy. Evaluations were conducted using standardized photography with live assessments performed by trained dermatologists. Wrinkle score was graded on a published validated 5-point scale (Croma Dynamic Forehead Lines-Assessment Scale) [18], ranging from grade 1 for no winkles to grade 5 for very severe wrinkles. Permission to use the Croma Dynamic Forehead Lines-Assessment Scale was obtained from Croma-Pharma GmbH prior to the commencement of this study. The scale was used with authorization for research purposes in accordance with the publisher’s guidelines. Data collection spanned the duration of the study (169 days), with measurements taken at rest and in a dynamic state.

As early as week 2, 92% of the subjects showed an improvement in the severity of FHL by 1 point. For our primary endpoint, this was 100% for Ona-BoNTA and Abo-BoNTA and 96% for Leti-BoNTA. The 1-point improvement was observed in more than 50% of subjects by the end of the study (Fig. 5).

Fig. 5.

A ≥ 1-point improvement in forehead line severity within 24 weeks

A 2-point improvement was observed at week 2 in over 60%, at the primary endpoint in over 75%, and at the end of the study in around 10% of subjects.

There were no significant differences in forehead line severity and wrinkle reduction within the formulations for each visit (Fig. 6).

Fig. 6.

A ≥ 2-point improvement in forehead line severity within 24 weeks

Discussion

Leti-BoNTA is a botulinum toxin derived from the CBFC26 strain of Clostridium botulinum, first approved in Korea in 2012 for the treatment of glabellar lines and now approved in over 65 countries [8]. It shares identical 16S RNA and protein sequences with Ona-BoNTA but undergoes additional purification steps, including enzyme-free nucleic acid removal, to enhance quality and reduce potential immunogenic impurities [19].

The present study aimed to compare the efficacy and diffusion characteristics of Leti-BoNTA, Ona-BoNTA, and Abo-BoNTA in the treatment of forehead lines and wrinkle severity. The maximal area of anhidrosis was significantly larger for Ona-BoNTA and Abo-BoNTA compared with Leti-BoNTA. Specifically, the mean difference in maximal anhidrotic area from Leti-BoNTA to Ona-BoNTA was −15.1 ± 5.5 cm² and to Abo-BoNTA was −25.2 ± 14.5 cm², both reaching statistical significance (p < 0.001). This suggests a lower diffusion capacity under standardized conditions, which may translate into a more confined therapeutic effect. Such a profile could be particularly relevant in anatomical regions where precise localization is desired to reduce the risk of diffusion-related adverse effects. At the same time, it is important to note that more limited diffusion may also affect the extent of muscle coverage, particularly in broader treatment areas.

However, all subjects responded positively to BoNTA injections, confirming the expected biological activity of the tested formulations [20] and indicating that a more localized area of effect does not necessarily jeopardize clinical outcome. These results are limited to the used doses, including the dose conversion ratio of 1:2.5 onabotulinumtoxinA: abobotulinumtoxinA, and injected volumes [14]. It should be noted that volumetric dilution and injection technique, both of which are known to influence BoNTA diffusion, were not systematically varied or analyzed in this study [5].

In addition to its effect on anhidrosis, the impact of BoNTA on wrinkle severity was evaluated. By week 2, 92% of subjects exhibited at least a 1-point improvement in forehead line severity, reaching 100% for Ona-BoNTA and Abo-BoNTA and 96% for Leti-BoNTA. A 2-point improvement was noted in over 60% of participants by week 2, in over 75% by the primary endpoint, and persisted in around 10% of subjects by the end of the study. These findings indicate that all three formulations effectively reduce wrinkle severity, despite differences in the maximal areas of anhidrosis, though the long-term efficacy appears to vary.

The AUC analysis over 6 months revealed significant differences in the accumulated anhidrotic effects. The mean AUC differences from Leti-BoNTA were −2056.7 d·cm² for Ona-BoNTA and −3172.6 d·cm² for Abo-BoNTA (p < 0.001). This indicates that Abo-BoNTA results in the largest overall anhidrotic effect, followed by Ona-BoNTA, whereas Leti-BoNTA demonstrates the least overall anhidrotic effect. These results align with previous studies indicating that Abo-BoNTA has a higher diffusion potential compared with Ona-BoNTA [21]. As Leti-BoNTA has been reported to be noninferior to Ona-BoNTA [8], these findings further support the hypothesis that Leti-BoNTA follows a similar trend.

While this study provides valuable insights into the comparative efficacy of Leti-BoNTA, Ona-BoNTA, and Abo-BoNTA, it is particularly noteworthy as the first diffusion study to include a FHL assessment. This approach addresses a key limitation of previous studies by allowing a direct correlation between anhidrotic effects and muscle paralysis. Nevertheless, certain limitations must still be considered. The sample size was relatively small, and the loss of four subjects to follow-up may have influenced the final results. Although the relatively high dropout rate of 13% was not explicitly addressed in the outcome analysis, it may have affected the statistical power of the study. Additionally, individual variability in response to botulinum toxin could not be entirely controlled. To enhance the robustness and generalizability of the findings, future studies with larger cohorts and extended follow-up periods would help to further validate these findings.

With injection in accordance to the C-line [22], Leti-BoNTA did not pose any risk of eyebrow ptosis or other adverse effects. Although it exhibited lower diffusion characteristics compared with the other formulations, it demonstrated equivalent clinical efficacy; however, the implications for long-term outcomes and broader indications remain to be further investigated. This suggests that Leti-BoNTA is a precise and targeted toxin with predictable diffusion properties, making it a viable option for applications where controlled diffusion is essential—without being limited solely to wrinkle reduction.

Conclusions

Overall, our findings demonstrate that all three botulinum toxin formulations effectively induce anhidrosis. Despite significant differences in their diffusion characteristics, they exhibit comparable improvements in wrinkle severity. These results suggest that the choice of formulation should be tailored to the desired clinical outcome—particularly in applications where predictable diffusion with effective wrinkle reduction are essential. Conversely, this also implies that injection points should be selected according to individual diffusion profiles to achieve optimal clinical outcomes and high responder rates.

Author Contributions

All authors contributed to the study conception and design. Material preparation, data collection, and analysis were performed by Maxine Bennek, Daniela Rudowitz, and Martina Kerscher. The first draft of the manuscript was written by Maxine Bennek, and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Funding

This research and the Rapid Service Fee were funded by Croma-Pharma GmbH, Leobendorf, Austria.

Data Availability

The datasets generated and analyzed during the current study are not publicly available owing to participant privacy and confidentiality agreements but are available from the corresponding author on reasonable request.

Declarations

Conflicts of Interest

Maxine Bennek reports no conflicts of interest. Daniela Rudowitz is employed by Croma-Pharma GmbH. Martina Kerscher has served as a speaker and/or advisory board member for AbbVie/Allergan, Merz Aesthetics, Croma-Pharma GmbH, Ipsen, Neauvia, Galderma, and Nordberg Medical.

Ethical Approval

The study (EU CT: 2024-511047-26-01) was conducted in accordance with the Declaration of Helsinki and Good Clinical Practice (GCP) guidelines. The research protocol was reviewed and approved by the Ethics Committee of the Medical Association of Munich (Ethikkommission bei der Medizinischen Fakultät der Ludwig-Maximilians-Universität München, Pettenkoferstraße 8, München). All participants provided written informed consent to participate in the study. Consent for publication was obtained from all participants for whom identifiable data are included. All participants provided written informed consent for publication.