Inhaled Aviptadil Is a New Hope for Recovery of Lung Damage due to COVID-19

In late December 2019, SARS-CoV-2 emerged and started a pandemic causing thousands of new cases due to new variants that are spread globally [1]. COVID-19 defines the disease caused by this virus which can affect multiple organs, thus causing a wide range of clinical outcomes, from asymptomatic to fatal [2, 3]. Symptoms such as fever, cough, and shortness of breath have been the most commonly reported due to the primary lung involvement in the majority of cases [2, 3]. Despite enormous efforts and investments, effective antiviral and adjunctive treatments have remained limited. Moreover, 67% of the world population have completed primary vaccine series and only 32% of them have been boosted [4, 5]. Due to the immunity elicited through vaccination and/or infection, the disease course is now benign in immunocompetent adults, but severe course of SARS-CoV-2 still affects risk groups like immunocompromised and older adults. Therefore, there is still a need for finding new treatment strategies.

It has been shown that the SARS-CoV-2 virus enters the type 2 pulmonary alveolar cells by binding to the angiotensin-converting enzyme 2 receptors and then leads to cytokines’ release which destroys these cells and impairs the alveolar gas exchange [6, 7]. The type 2 pulmonary alveolar cells are capable of surfactant production. Also, they can self-renew and even replace the damaged alveolar epithelium by differentiating into type 1 pulmonary alveolar cells which are also a part of the alveolar unit, responsible for gas exchange [8]. Vasoactive intestinal peptide (VIP), which is an endogenous peptide, has been shown to target the VIP receptor 1 (VPAC1) on alveolar type II cells and provide lung-protective effects. Preclinical studies have found that VIP can even inhibit SARS-CoV-2 RNA replication [9, 10]. We hypothesized that VIP might be a promising treatment option against the COVID-19 pneumonia. Several clinical studies have been conducted on the use of aviptadil, which is a synthetic form of VIP, in the treatment of COVID-19. In all these studies, aviptadil was administered intravenously to critically ill COVID-19 patients with respiratory failure. One study with 196 patients who had a critical COVID-19 respiratory failure did not show a significant change for improvement when compared to placebo but did improve the likelihood of survival at day 60 [11]. The TESICO study also showed no significant clinical improvement with intravenous aviptadil after 90 days from treatment compared to placebo [12]. Both these studies involved severe patients who needed either mechanical or noninvasive ventilation, high-flow oxygen, or extracorporeal membrane oxygenation, which are associated with a severely ill group in clinical practice. Moreover, intravenous administration of aviptadil may lead to premature loss-of-efficacy before reaching its target (i.e., pneumocytes) and result in excess off-site reactions. Delivery of a drug that is known to have systemic adverse effects, via inhalation to the lungs, is a frequently utilized method to minimize the side effects of the drug and to ensure its direct effectiveness at the site of action [13]. Boesing et al. [14] designed a clinical trial for treatment of COVID-19 patients at high risk for acute respiratory distress syndrome (ARDS) by inhaled aviptadil treatment for 10 days, but the study was terminated early this year due to difficulties in recruiting suitable participants and results were not published.

The objectives of this study were to investigate the short- and long-term effects of inhaled aviptadil on adult COVID-19 patients who were hospitalized due to the need for supplementary oxygen and pneumonia, but did not need intensive care at admission. To achieve this objective, a multicenter, prospective, placebo-controlled, comparative, randomized, double-blind, phase II clinical trial was conducted and evaluated.

This phase II, prospective, randomized, double-blind, and placebo-controlled clinical trial aims to compare the effectiveness of aviptadil with a placebo in treating lung damage due to SARS-CoV-2 infection. This study took place at nine tertiary centers that were actively involved in COVID-19 patient care. The time of recruitment of the patients was between 10 March 2021 and 7 June 2022. It involved eight visits, from which seven were face-to-face and one was a remote follow-up visit. The study recruited patients who were 18 years or older and had been hospitalized due to their respiratory symptoms and pneumonia caused by COVID-19. A total of 80 patients were randomly divided into two groups with a 1:1 ratio. Patients who were eligible for participation in the study received standard medical treatment for SARS-CoV-2 infection as indicated by the national guidelines along with either aviptadil or placebo. The complete list of inclusion and exclusion criteria can be found in online supplementary material (for all online suppl. material, see https://doi.org/10.1159/000543773).

The study was approved by the Institutional Review Board of Baskent University Hospital (KA20/460), and regulatory approval was issued by the Ministry of Health (2020-11-30T16_43_59). Written informed consent for trial participation was obtained from each enrolled participant. The study was conducted in accordance with the Declaration of Helsinki.

The treatment and placebo arms were as follows.

The patients inhaled 2 mL aviptadil solution (as 100 μg/mL solution, two consecutive doses 1 mL each, 30 min apart once a day during lunch time) by mesh nebulizer + standard of care (antiviral drug favipiravir treatment involves a loading dose of 1,600 mg BID followed by a maintenance dose of 600 mg BID for a total of 5 days).

The patients inhaled 2 mL saline placebo (same as aviptadil solution) by mesh nebulizer + standard of care. Both the treatment and placebo vials were identical regarding appearance, smell, or the amount administered. Patients who required admission to intensive care after recruitment due to disease progression were withdrawn from the study and continued treatment in the intensive care unit (ICU) as deemed appropriate by the physician. The inhalation of aviptadil/placebo was administered for a minimum of 7 and a maximum of 14 days to all the patients. For patients, whose symptoms did not improve after the treatment administered for 14 days, aviptadil/placebo was discontinued.

Patients’ visits were scheduled to assess their clinical, laboratory, and radiological status together with the assessment of possible adverse effects. There were 8 visits which were arranged as follows: visit 1 on day 1 (at admission), visit 2 on day 3, visit 3 on day 7, visit 4 on day 10, visit 5 on day 14 (up to this visit, patients were evaluated as inpatients or in some cases as outpatients if they were discharged after day 7), visit 6 on day 28 (as outpatient), visit 7 on day 90 (this visit was remote, by phone), and last visit 8 on day 180 (as outpatient). The clinical evaluation included medical history, measuring vital signs such as body temperature, blood pressure, respiratory rate, saturation assessment by noninvasive methods such as pulse oximetry, heart rate, physical examination, and dyspnea evaluation was done by using the modified Borg scale [15, 16]. Laboratory investigations were performed on days 1, 3, 7, 10, 14, and 28, respectively. Radiological evaluation was assessed by thorax computed tomography (CT) at admission (day 1), on day 28, and at the end of 6 months (day 180). See Figure 1.

The main effectiveness measurement of the study and the primary outcome is the time from hospitalization to discharge, which is defined as days of hospitalization within 30 days of initial treatment. The safety population included all patients who received at least one dose of the investigational product and underwent at least one follow-up visit, whether as inpatient or outpatient. Throughout the study, safety assessments were performed through physical examinations, monitoring of vital signs, and clinical laboratory tests. Any abnormal findings considered clinically significant according to the protocol criteria were recorded as adverse or severe events.

Chest CT scans were performed at initial diagnosis, at 1-month (day 28) and 6-month (day 180) follow-ups. Some of the patients who refused or could not have a CT scan done at the planned visit led to a decrease in the number of patients who were involved in the CT evaluations (44 out of 80 for day 1, 50 out of 58 for day 28, and 49 out of 50 for day 180, respectively). Patients were positioned supine with raised arms and instructed to hold their breath during scanning. CT scans of the chest were taken from the apex to the lung bases.

A radiologist (G.D.) with 16 years of experience evaluated the CT images blindly without access to clinical data. The examinations were classified as typical or indeterminate according to the Radiological Society of North America (RSNA) classification system for COVID-19 pneumonia [17]. A CT score was calculated based on the extent of opacities, including ground-glass opacity, crazy paving pattern, and consolidation, in each lobe. Scores ranged from 0 (no opacities) to 5 (opacities affecting >75% of the lobe), with a maximum score of 25 for all five lobes combined [18]. Additionally, CT findings such as ground-glass opacity, consolidation, crazy paving pattern, subpleural band, interstitial thickening, and fibrosis were noted for each patient.

Patients were evaluated for the severity of their dyspnea at admission (day 1), day 7, and day 28 visits. The score was assigned according to patient report in a 0–10 scale as reported previously [15, 16].

Randomization was performed using the block randomization method using R 4.0.1 (www.r-project.org) software. A total of 8 blocks with a size of 10 were used. In this way, a balanced distribution of drug groups was ensured within each block. While calculating the sample size, it was evaluated that the treatment would be effective on the minimum differences to be obtained over the SpO₂ percentage of the individuals who would participate in the study. At the time of planning this study, no similar study was available to which could be used as a reference, so we mainly focused on the prediction of saturation values in order to foresee the clinical prognosis and possible drop-outs.

The power analysis was performed, and for power 80% and 90%, the patients’ number to be included in each group was calculated as 22 and 28, respectively. Taking into consideration drop-outs that might occur after recruitment at a range up to 30%, the total number for recruitment was calculated as 80 patients (40 patients in each group).

The conformity of numerical variables to normal distribution was examined with the Shapiro-Wilk and Kolmogorov-Smirnov normality tests. Numerical variables were presented as mean ± standard deviation and median values (with minimum-maximum), and categorical variables as the number and percentage. Since the variables were not normally distributed, the Wilcoxon test was used to compare the differences between dependent groups and Mann-Whitney U for the independent ones. Statistical analyses were performed using SPSS version 25.0 software for Windows. The statistical significance level was set as 0.05 in all tests.

This study is a multicenter investigation based on real clinical data. Consequently, we did not use imputation methods or other techniques to handle missing data. Instead, analyses were performed based on the available data. The number of observations with missing data for each variable has been clearly presented in the tables to ensure transparency.

The recruitment plan used in the study has been presented in Figure 2. The gender, age, and vital sign distributions were comparable between the aviptadil and placebo groups (p > 0.05) (online suppl. Table 1). Even after considering the drop-out patients, the distributions remained similar between the groups. The measurements of SpO₂ of patients that could not tolerate removal of oxygen support were measured while on supplementary oxygen.

A total of 11 patients experienced worsening symptoms and progressive disease during their hospitalization period and were consequently admitted to the ICU. ICU admission was 10.3% and 17.1% of patients in the aviptadil and placebo groups, respectively (p = 0.376). The average discharge time was 7.8 ± 4.0 days in the aviptadil group compared to 10 ± 5.0 days in the placebo group (p = 0.049). Since all the patients were discharged within 30-day period regarding the primary outcome, the rate of discharge was similar for both groups (89.7% for aviptadil and 82.9% for placebo, p = 0.376).

The results showed that on the seventh day of treatment, patients in the aviptadil group had a significantly lower total score on the modified Borg scale compared to the placebo group (p = 0.033). However, on day 28, there was no significant difference between the two groups (p = 0.144; Table 1).

We also compared the changes in lung parenchyma. The initial CT lung damage score was comparable within the study groups at admission (p = 0.962). Follow-up CT scans on day 28 revealed a lower score in patients receiving aviptadil (p = 0.028) (Table 2).

Chest CT scans in aviptadil group patients demonstrated lower scores on day 28 and day 180 (p = 0.003 and p < 0.001, respectively; online suppl. material Table 2). Representative images of CT scans for both placebo and aviptadil group are shown in Figure 3. The 180-day mortality was 5.1% (2 patients) in the aviptadil group versus 12.2% (5 patients) in the control group (p = 0.433).

During the study, for both aviptadil and placebo groups, 51 adverse events were reported, with most common being the elevation of liver enzymes, such as alanine transaminase and lactate dehydrogenase, along with increased C-reactive protein (CRP) levels (online suppl. material Table 3). Hypoxia was frequently reported (a total of 11 cases) as a severe adverse effect, and it was more common in the placebo group. Elevated CRP and progression of hypoxia were deemed not to be related to the study intervention, but to the COVID-19 disease progression. The total mortality rate was 8.8% (a total of 7 patients out from 80; 2 from aviptadil; and 5 from the placebo group). Although not all serious adverse events were deemed to be related to the investigational product, patients did not withdraw from the study due to a severe adverse event. The safety assessments of both groups indicated that aviptadil could be considered a safe and tolerable treatment option.

Results of this phase II study showed inhaled aviptadil along with the standard care decreased the hospitalization duration and enabled a faster improvement of both dyspnea and the radiological findings of hospitalized COVID-19 patients. The vital role of alveolar type 2 cells in the lungs in maintaining the integrity, function, and healing of the alveoli is well known [8]. In COVID-19 patients, it has been discovered that the SARS-CoV-2 virus enters these cells through the ACE2 surface receptor, leading to cell death and lung damage that can prove fatal [7, 19]. If the damage does not reach a fatal point, long-term effects of COVID-19 can occur, resulting in persistent symptoms of the disease [20]. Preclinical studies involving VIP during COVID-19 have shown that it can inhibit SARS-CoV-2 RNA synthesis, and elevated levels of VIP in serious COVID-19 patients have been linked to decreased inflammatory mediators and improved survival rates [9, 10]. Moreover, VIP has demonstrated lung-protective and immunomodulatory effects by binding to its receptor VPAC1, which is also present in the alveolar type 2 cells in the lungs [21]. An effective intervention should protect type 2 alveolar cells from the damage caused by the SARS-CoV-2 virus infection. It would be crucial that this treatment is used before the type 2 alveolar cells become completely injured, which might be the case for critically ill patients who develop ARDS and that the amelioration of alveolar epithelium can occur due to the stem cell feature of the type 2 cells which can renew and replace even the type 1 alveolar cells, thus leading to improved gas exchange.

Previous clinical studies with aviptadil have been performed in critically ill patients who needed invasive or noninvasive mechanical ventilation, high-flow oxygen, or extracorporeal membrane oxygenation and who were admitted to the ICU at the time of the treatment [11, 12]. This group of patients has a high risk for a worse outcome and high mortality. Thus, the features of the patients included might have been the main cause that a significant difference regarding the clinical outcome was not reached at 60 and 90 days in previous trials [11, 12]. On the other hand, even though in a very limited number of patients intravenously administered aviptadil was shown to improve the clinical outcomes in patients with virus-related ARDS arising from other viruses apart from COVID-19 [22, 23].

Our results suggest that inhaled aviptadil is well tolerated as no intervention-related discontinuations were detected. Aviptadil has previously been administered in two different routes, intravenously or inhalation [11, 12, 24‒27]. In previous trials, aviptadil was administered intravenously, which might have been the main reason for the excess adverse effects such as hypotension (due to its vasodilator nature) and grade 3 or 4 diarrhea (due to aviptadil’s intestinal effects) [12]. There is even a case report that showed that intravenous aviptadil not only led to rapid clinical improvement but was also safely used in a pregnant patient with COVID-19-related respiratory failure [28].

Aviptadil has also been investigated in various lung diseases like pulmonary hypertension via inhalation [26]. The posology implemented in this trial was based on the pharmacokinetic properties of aviptadil, which showed that the VIP dispersed from the blood to the tissues in 5 min and then accumulated in the lungs, where it remained for 24 h. Thus, we aimed to achieve a high peak level by applying two consecutive doses with 30 min apart, which was also easily taken by the patients with no need for further doses during the day. The mesh nebulizer could be easily applied, and cooperation was easy, thus suggesting that this could also be a possible home-based treatment. Calfee et al. [27] showed no benefit of inhaled aviptadil in critically ill patients, and this might be a result of difficulty applying the inhaled drug to patients with high oxygen need or who are in mechanical ventilatory support and reduce significantly the intake of the drug.

This study showed a rapid clinical improvement in aviptadil group with a shorter discharge period. It is important to show the radiological changes as well in order to have a prediction of lung function and lung sequelae afterward. Follow-up CT imaging was used to evaluate the disease recovery. On day 28, the improvement in the radiological findings of the aviptadil group was statistically significant compared to the placebo group. This highlights the importance of inhaled aviptadil treatment for fast recovery and the possible reduction of sequelae formation and long-term COVID-19 symptoms. To our knowledge, this is the first study to show a radiological improvement in COVID-19 patients with pneumonia due to aviptadil treatment.

However, there are some limitations of this study. Even though this is a multicenter clinical trial, due to drop-outs, the number of patients enrolled and who could complete the study is low to generalize the results. Thus, even though power analysis calculations were performed before the study, a larger sample size might have helped achieve more significant results for a power of 95% (for placebo 22 patients reached 80%, whereas the aviptadil group of 28 reached 90% power). Another limitation is the measurement of SpO₂ for some patients who could not tolerate removal of oxygen and the recordings were made while on supplementary oxygen, thus influencing the mean value.

Our study focused on patients who do not require intensive care but needed hospitalization and supplementary oxygen. This group is the most common group of patients that we encounter in our clinical practice, and with early and proper intervention, it can be cured and cannot progress to severe or long COVID disease. The main reason for the insignificant results of some studies might be attributed to the mechanism of action of aviptadil, which may not be effective in repairing already severely damaged lung cells for the critically ill patients. Additionally, aviptadil is a peptide that carries the treatment signal rather than an antiviral drug, and choosing this as the treatment target for patients with advanced lung damage may be another factor contributing to the failure of previous studies. The early inhalation of aviptadil in COVID-19 patients and its ease of usage might be important for future treatment options, and phase III studies are needed to generalize our findings.

This phase II clinical research study is the first to investigate the effect of inhaled aviptadil on hospitalized patients due to SARS-CoV-2 pneumonia. The study demonstrated that adding aviptadil inhalation to standard treatment could reduce hospitalization duration and result in a faster improvement in both dyspnea score and CT findings compared to standard treatment plus placebo. Additionally, safety parameters in both groups suggest that aviptadil could be a safe and easily applied supplementary intervention. Further studies are needed to show if this treatment might help reduce lung sequelae or post-COVID-19 symptoms.

The authors thank Sedat Altug from Monitor CRO (Istanbul, Turkey), Adem Sahin from Centurion Pharma (Istanbul, Turkey), and Irem Unsal, DVM, from Monitor CRO (Istanbul, Turkey) for their contribution to medical writing and editorial assistance. All statistical calculations and analyses were performed by Monitor CRO.

The study was approved by the Institutional Review Board of Baskent University Hospital (KA20/460), and regulatory approval was issued by the Ministry of Health (2020-11-30T16_43_59). Written informed consent for trial participation was obtained from each enrolled participant. The study was conducted in accordance with the Declaration of Helsinki. This clinical trial was registered before patient enrolment. This trial has been registered at ClinicalTrials.gov with an ID of NCT04844580.

The authors have no conflicts of interest to declare.

This study was funded by Centurion Pharma. The funder had no role in the design, data collection, data analysis, and reporting of this study.

Dorina Esendagli, Erdoğan Çetinkaya, and Ahmet Çağkan İnkaya have participated in study design and protocol of the study. Dorina Esendagli had full access to all of the data in the study, took responsibility for the integrity of the data and the accuracy of the data analysis, and wrote the paper. Ahmet Çağkan İnkaya has revised the manuscript. All the authors have contributed in acquisition of data, analysis, and interpretation together with the reporting of adverse effects and approved the final version of the article.

The data that support the findings of this study are available on request from Dorina Esendagli.