FormalPara Key Summary Points

Nintedanib is a potent tyrosine kinase inhibitor, approved by the Food and Drug Administration and Drugs Controller General of India (DCGI) for idiopathic pulmonary fibrosis (IPF) management.

Nintedanib has been shown to be an effective therapeutic option with an established safety profile in IPF in numerous randomized placebo-controlled trials as well as real-world evidence studies.

It helps stabilize the disease progression in patients with interstitial lung disease (ILD) and slows the rate of forced vital capacity (FVC) decline in a variety of patient subgroups, including those with comorbidities such as obesity, type 2 diabetes, cardiovascular problems, and emphysema.

Patients on nintedanib treatment may have gastrointestinal adverse events that tend to be of mild to moderate severity.

Introduction

Interstitial lung diseases (ILDs) represent a broad group of lung disorders, categorized into those with known causes and with unknown causes, known as idiopathic interstitial pneumonias (IIPs) [1]. Idiopathic pulmonary fibrosis (IPF) is a most common type of idiopathic interstitial pneumonia (IIP) and severe form of ILD that is marked by progressive fibrosis and scarring in the lungs. Another form of progressive and fibrotic condition observed in ILD is progressive pulmonary fibrosis (PPF), which shares similar underlying mechanisms and disease patterns with IPF [2]. The precise etiology of IPF remains elusive, however, risk factors including tobacco use, genetic predisposition, toxin exposure, viral infections, and abnormal immune responses are thought to play a role in its pathogenesis. The adjusted prevalence of IPF varies between 0.33 and 4.51 per 10,000 individuals worldwide [3]. In Asia–Pacific nations, the estimates ranged from 0.57 to 4.51/10,000; corresponding figures in North America and Europe range from 2.40 to 2.98 and 0.33 to 2.51, respectively. Based on these prevalence estimates, IPF is categorized as a rare disease [3]. As per an ILD-India registry report that included 1084 patients from 27 study centers across India, 148 (13.7%) were diagnosed with IPF [4]. According to the recent retrospective analysis of data obtained over a 5-year period from individuals suffering from ILD, of the 517 subjects with ILD, 87 (21.3%) were incident cases of IPF. The estimates for the crude annual incidence and prevalence rates of IPF per 100,000 population were 2.1–4.3 and 5.8–11.6, respectively, with a crude national burden in the range of 51,000 to 102,000 [5].

Previously, the focus of IPF therapy was directed at the reduction of inflammation supposedly to halt its progression to fibrosis [6]. However, observations suggest that IPF is primarily marked by fibrosis rather than inflammation, thus anti-inflammatory therapy results in a poor prognosis [6]. Clinical studies have lately redirected their attention from anti-inflammatory and immunosuppressive medicines towards novel compounds with antifibrotic properties such as nintedanib and pirfenidone. The efficacy and safety of nintedanib have been established in slowing the loss of forced vital capacity (FVC) in patients with IPF who have mild-to-moderate functional impairment [7, 8].

This review discusses the underlying physiological processes of IPF and the mechanism of action of nintedanib in IPF. It evaluates the effectiveness and tolerability of nintedanib in patients with IPF, with a particular focus on patient subgroups, including those with comorbidities, treatment non-adherence, and newly diagnosed cases. Additionally, the review addresses strategies to improve treatment outcomes and manage adverse events (AEs), further discussing the choice of one antifibrotic over another. This article is based on previously conducted studies and does not contain any new studies with human participants or animals performed by any of the authors.

Pathophysiology of IPF

Several factors are believed to play a role in the pathophysiology of IPF, including genetic predisposition, environmental factors, and aberrant wound healing responses, leading to progressive lung tissue fibrosis. Repetitive micro-injuries to the alveolar epithelium initiate the disease, triggering a dysregulated wound healing response involving various cells and extracellular matrix components (ECM) [9]. In response to epithelial injury, an aberrant repair process is initiated and abnormally activates fibroblasts, transforming them into myofibroblasts, leading to excessive collagen production and scar tissue formation in the lungs. Fibroblasts are normally responsible for producing the ECM that gives structural support to tissues. However, this kind of abnormal activation of fibroblast causes the deposition of excessive amounts of ECM proteins, including collagen, into the lung interstitium, leading to the formation of scar tissue or fibrosis [10]. Myofibroblasts lead to remodeling and stiffening of the lungs’ tissues. Inflammation, abnormal cell interactions, and vascular abnormalities further perpetuate fibrosis and disrupt lung function (Fig. 1).

Fig. 1
figure 1

Pathophysiology of idiopathic pulmonary fibrosis. ATP adenosine triphosphate, FGF fibroblast growth factor, FGFR FGF receptor, ILD interstitial lung disease, IPF idiopathic pulmonary fibrosis, PDGF platelet-derived growth factor, PDGFR PDGF receptor, TGF-β transforming growth factor beta, VEGF vascular endothelial growth factor, VEGFR VEGF receptor

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Management of IPF

Treatment options for IPF include both non-pharmacological and pharmacological approaches. The non-pharmacological approach consists of supportive care measures including smoking cessation, pulmonary rehabilitation, maintaining a healthy weight, cough management, vaccinations to prevent complications, low-dose narcotics, and supplemental oxygen. The other options include palliation and lung transplantation, which may prolong survival [6].

There have been substantial changes in the treatment strategy for IPF during the last two decades. In the past, the conventional approach for treating patients with IPF has been the use of corticosteroids and immunosuppressive drugs such as triple combination therapy of prednisone, azathioprine, and N-acetylcysteine. This treatment strategy was rooted in the hypothesis that the development and progression of pulmonary fibrosis may be preceded by chronic inflammation. Nevertheless, the PANTHER-IPF trial (NCT00650091), which was early terminated due to notable escalation in mortality and hospitalization rates, presented strong evidence against the use of the triple combination therapy for patients diagnosed with IPF and exhibiting mild-to-moderate impairment in lung function [11]. Other immunomodulatory agents like mycophenolate mofetil and cyclophosphamide have no clinical benefit in patients with IPF and are contraindicated for IPF management [12, 13].

The transition away from immunosuppression resulted in a therapy gap when there were no effective alternatives available. However, in October 2014, the Food and Drug Administration (FDA) approved two antifibrotic agents namely, nintedanib and pirfenidone, for IPF management. Both these drugs have also been approved by Drugs Controller General of India (DCGI) for use in patients with IPF in 2016 and 2010, respectively [14]. Nintedanib also got DGCI approval for the management of systemic sclerosis-associated interstitial lung disease (SSc-ILD) in adults in 2020 [15]. These agents have shown effectiveness in reducing the rate of FVC decline over one year among individuals with lung dysfunction of mild to moderate severity. In 2020, nintedanib was approved by the FDA for use in chronic fibrosing ILD. Other novel therapies such as intravenous infusion of lung stem cells, pentraxin, pamrevlumab, GLPG1690 (autotaxin inhibitor), galectin‐3, and human antigen R may be promising therapies for IPF in the future [16].

Guideline recommendations for the management of IPF

There are several treatment guidelines that have recommended these treatments for the management of IPF, and the updated version of the guidelines is summarized in Table 1. The present evidence-based recommendations for the treatment of IPF advocate the use of nintedanib and pirfenidone.

Table 1 Guideline recommendations for the IPF treatment
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Moreover, the National Health Scheme (NHS) IPF and the National Institute of Health and Care Excellence (NICE) also provided their expert recommendations for managing IPF. According to the NICE guidelines, 2016, nintedanib was recommended in individuals having an FVC between 50% and 80% predicted, and if nintedanib is accessible to the patient at a discounted rate through a patient access scheme [17]. However, recent NICE Technology Appraisal, 2023, recommends nintedanib to treat IPF in patients with FVC > 80% predicted [18]. They also emphasize the importance of discontinuing the treatment in the case of disease progression or intolerable side effects. The standard dose is 150 mg taken twice daily, approximately 12 h apart, with an option to reduce it to 100 mg twice daily if necessary [19]. Furthermore, the Scottish Medicines Consortium (SMC) also approves nintedanib for restricted use in adults with IPF, especially those with a predicted FVC > 80% [20]. It should be noted that nintedanib was previously approved by SMC for those who have a predicted FVC ≤ 80% [20]. This recommendation is based on the observed reduction in the decline of pulmonary function when compared to a placebo [20].

Nintedanib: A Potent Triple Angiokinase Inhibitor

Nintedanib (BIBF1120) is a tyrosine kinase inhibitor that works by inhibiting multiple receptor tyrosine kinases that are involved in various key signaling pathways like angiogenesis and fibroblast activation, thus significantly reducing the progression of disease. It specifically targets angiogenesis of endothelial cells, pericytes, and smooth muscle cells and effectively suppresses cell proliferation and induces apoptosis.

Furthermore, it inhibits fibroblast activation by blocking the activity of receptors associated with growth factors such as fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF). Nintedanib-induced reduction in the activity of these profibrotic mediators in turn prevents excessive fibrosis or scar tissue formation, which is a characteristic feature of IPF (Fig. 2) [21]. Nintedanib exhibits competitive binding to the intracellular adenosine triphosphate (ATP) binding site of growth factor receptor kinase domains of VEGFR 1–3, PDGFR-α and -β, and FGFR 1–3, hence impeding tyrosine kinase activity, autophosphorylation and obstructing subsequent signaling cascades [22]. Nintedanib also has inhibitory effects on non-receptor tyrosine kinases, such as Src and lymphocyte-specific protein tyrosine kinase (Lck), thereby providing a holistic reduction in the activation of fibroblasts [22]. As a result, the final action of nintedanib is the blocking of proliferation and migration of fibroblast, thus leading to a significant reduction in angiogenesis in the lungs. This further contributes to the inhibition of disease progression in ILD, IPF, and related consequences such as pulmonary hypertension, microangiopathy, and fibrosis [22, 23]. Nintedanib's antifibrotic potential is evident in various preclinical models, reducing lung collagen, fibrosis, inflammatory cell counts, cytokine levels, and fibroblast activation in systemic sclerosis models [23]. The recent Safety and Efficacy of Nintedanib in Systemic Sclerosis (SENSCIS) trial has demonstrated a significant effect of nintedanib on lowering the rate of decline in lung function in SSc-ILD [24].

Fig. 2
figure 2

Mechanism of action of nintedanib. ATP adenosine triphosphate, FGF fibroblast growth factor, ILD interstitial lung disease, IPF idiopathic pulmonary fibrosis, PDGF platelet-derived growth factor, VEGF vascular endothelial growth factor

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Pharmacokinetics of Nintedanib

Nintedanib is extensively distributed into peripheral tissues. It is metabolized through hydrolytic ester cleavage, leading to the formation of the free acid moiety, BIBF 1202, which is subsequently glucuronidated to form BIBF 1202 glucuronide [25]. Nintedanib exhibits low absolute bioavailability (4.69%) and increased solubility under acidic conditions (pH < 3). Taking nintedanib with food increases exposure by about 20% and delays absorption, enhancing gastrointestinal tolerability [25]. The likelihood of medication interactions occurring between nintedanib and other treatments that affect CYP enzymes (such as CYP inhibitors and CYP inducers) is very low [25]. It can be coupled with several IPF (like pirfenidone and bosentan) and chemotherapy medications [25]. However, caution is suggested when combining nintedanib with potent inhibitors or inducers of P-glycoprotein (P-gp) along with administration in patients with hepatic impairment [25]. The pharmacokinetic parameters of nintedanib are given in Table 2.

Table 2 Pharmacokinetic parameters after single oral administration of nintedanib 150-mg capsule under fasted and fed conditions to healthy male volunteers
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Efficacy of Nintedanib in Patients with IPF

The initial evidence of nintedanib efficacy in treating IPF was taken from TOMORROW trial [7]. This trial played a crucial role in establishing the drug's efficacy, ultimately leading to its approval for the treatment of IPF [7]. The results obtained from the TOMORROW trial influenced the design of the INPULSIS® trials, which included two replicate trials, INPULSIS®-1 and INPULSIS®-2. The combined data from these trials suggest that nintedanib has a consistent effect on reducing the rate of FVC decline over 24 weeks, regardless of the severity of gas exchange impairment. This finding supports the use of nintedanib in patients with advanced IPF. The details of these landmark studies on nintedanib are summarized in Table 3. The exploratory analysis of six prospective trials involving patients with IPF indicated that nintedanib has the potential to increase their life expectancy [26]. The estimated mean survival was found to be 11.6 years for patients treated with nintedanib, while those treated with placebo had a mean survival of 3.7 years [26].

Table 3 Clinical trials associated with efficacy outcomes of nintedanib
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Long-Term Efficacy of Nintedanib

For assessing the long-term efficacy of nintedanib, two additional studies, the open-label extensions of the TOMORROW trial [27] and the INPULSIS®-ON trial [28], have provided valuable insights. In the TOMORROW open-label extension trial, nintedanib continued to demonstrate sustained improvement and benefits in patients with IPF by significantly slowing down the progression of the disease beyond the initial 52 weeks with no new safety signals identified for a total treatment period of up to 86 months [27]. The INPULSIS®-ON trial's open-label extension results were consistent with the original INPULSIS® trials, showing a continued reduction in the annual rate of FVC decline over the long term [28]. A subgroup analysis within the INPULSIS®-ON trial, focusing on Asian patients with IPF, underscored the lasting effect of nintedanib in slowing the disease progression [29]. These patients experienced a decline in FVC of only 127 ml/year over a 192-week period, maintaining an acceptable safety profile [29] (Table 2).

Efficacy of Nintedanib in IPF in Real-World Studies

The findings from the real-world studies align with prior observations made in clinical trials investigating the effects of nintedanib in individuals with IPF [30,31,32]. A real-world study of 244 patients in Greece demonstrated a 3-year survival rate of 59.4% after nintedanib treatment [30]. In a study by Brunnemer in 2018, the effectiveness of nintedanib was investigated in 64 patients for at least 3 months. Notably, at the 6-month mark following the initiation of nintedanib, a substantial 67% of the patients exhibited disease stability, measured by FVC, which was maintained in 62% after 9 months [32]. A real-world observational study from India, involving 76 patients with IPF demonstrated that nintedanib reduced the rate of annual decline in parameters such as FVC and diffusing capacity of the lungs for carbon monoxide (DLCO) along with an increase in the 6-min walk distance [33]. Importantly, the drug was well tolerated by the Indian patients with IPF, suggesting its potential benefits in the real-world clinical setting [33].

Efficacy of Nintedanib in Newly Diagnosed Patients with IPF

European Multipartner IPF registry (EMPIRE) data of 2492 newly diagnosed patients with IPF shows that 64.5% of these patients received antifibrotic therapy, amongst which 34.9% were prescribed nintedanib [34]. A study by Brunnemer et al. (2018) involving 64 patients with IPF demonstrated disease stabilization in terms of reduction in decline of FVC, amongst which 30% of patients were treatment-naïve i.e., received nintedanib as their initial treatment without prior therapy [32]. An exploratory study on 235 treatment-naïve patients with IPF, of which 102 received nintedanib reported improved survival rates in people with IPF in gender-age-physiology (GAP)-1 or TORVAN stage I, when compared to those with advanced IPF [35]. The influence of the timing of nintedanib initiation in 449 newly diagnosed patients with IPF was assessed in a retrospective observational study [36]. This study suggested that patients with IPF who promptly start nintedanib after their disease diagnosis may experience reduced hospitalization risk and lower medical costs compared to those who initiate nintedanib after 2–3 months [36].

Efficacy of Nintedanib in Patients with IPF and Comorbidities

Patients with IPF typically have lifestyle-related comorbidities, including hypertension, type 2 diabetes mellitus (T2DM), hyperuricemia, and hyperlipidemia, which can exacerbate the course of their disease, reduce quality of life, and decrease treatment adherence [37]. Kreuter et al., 2016 observed that the majority of the patients with IPF have ≥ 1 comorbidities. In his study, only 11.4% of patients had no comorbidities, 18.4% had 1 comorbidity while the others had more than 1 comorbidities, among which cardiovascular comorbidity was the most common [38]. Another Danish study demonstrated the presence of cardiovascular disease in 27% of patients with IPF, followed by pulmonary hypertension and depression in 21% each, ischemic heart disease and arterial hypertension in 18% each, and diabetes in 17% patients [39]. A recent subgroup analysis of the combined five trials’ data demonstrated hypertension (27.6%), diabetes (9.8%), and gastroesophageal reflux disease (GERD) (9.6%) as the most common comorbidities in individuals with < 5 comorbidities whereas hypertension (58.4%), GERD (38.8%), and hypercholesterolemia (22.0%) among patients with IPF and ≥ 5 comorbidities [37]. The impact of nintedanib in slowing the rate of FVC decrease was consistent across comorbidity categories [37] (Table 4).

Table 4 Effect of nintedanib in patients with IPF with associated comorbidities
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Nintedanib in Patients with IPF and T2DM

The association of T2DM with IPF is established [40]. There is a decline in lung function in diabetes that is thought to be the result of biochemical changes in lung connective tissue constituents, particularly collagen and elastin, as well as microangiopathy, further causing alveolar epithelial basal lamina thickening, and consequently impairing the lung capacity for carbon monoxide diffusion [40]. On the other hand, the prevalence of diabetes is estimated to be between 10% and 42% among patients with IPF [40].

Studies have shown the efficacy as well as tolerability of nintedanib in patients with IPF, high degree of lung function impairment and a multitude of comorbid conditions especially T2DM [32, 41, 42]. The findings of the German Compassionate Use Program (CUP) showed that T2DM was the second most frequent comorbidity (after hypertension) observed in 15% of the patients with IPF enrolled in the CUP [31]. In situations where most patients were not treatment-naïve and had comorbidities like T2DM, nintedanib treatment was generally well tolerated and led to FVC stabilization in 63% patients with IPF over 6 months [31].

Nintedanib in Patients with IPF and Cardiovascular Diseases

Obesity and related concomitant diseases such as acid reflux and pulmonary hypertension can also contribute to chronic hypoxemia, resulting in the production of proinflammatory cytokines and changes in the fibrotic pathway in the lungs [43]. Individuals diagnosed with IPF experience a substantial prevalence of CV disease with a notable overlap in risk factors between them, such as male gender, smoking history, and > 60 years of age [44]. Nearly 50% of the patients with IPF had hypertension, while one-third were presented with coronary artery disease [32]. Patients with IPF along with coronary artery disease and arterial hypertension exhibited a slower reduction in FVC compared to those without these comorbidities after 3, 6, and 9 months of nintedanib therapy [32]. The observed alterations in FVC among individuals diagnosed with both coronary artery disease and arterial hypertension indicate that nintedanib therapy is beneficial to these patients as well. Furthermore, combined data of TOMORROW and INPULSIS trials suggests that there was no significant difference in the occurrence of major adverse cardiovascular events and myocardial infarction between individuals receiving nintedanib and placebo [45]. Typically, experts suggest the use of nintedanib in patients with IPF and cardiac disease as comorbidity unless they need simultaneous anti-coagulant treatment [46].

Nintedanib in Patients with IPF and Emphysema

Patients diagnosed with lung cancer and IIP, including IPF, exhibit a higher prevalence of combined pulmonary fibrosis and emphysema (CPFE). The prevalence of CPFE ranges between 8% and 67% in patients with IPF and varies according to the population or geographical area, with the greatest estimates coming from Asia and Greece and the lowest from the United States [47]. Patients with IPF with comorbid emphysema had a smoking history of 22.5 pack-years, which was longer compared to those without emphysema, who had a smoking history of 14.9 pack-years [32].

Post-hoc analysis of pooled data of INPULSIS® trials did not find significant differences in treatment effect of nintedanib between patients with IPF and with or without emphysema [48]. However, Brunnemer et al. observed slightly higher (77.3%) mean FVC and lower (32.1%) mean DLCO in individuals with emphysema than without emphysema [32]. Various studies have also indicated that nintedanib was effective in stabilizing disease in patients with IPF, including those with emphysema, and that it was well-tolerated [41, 49].

Efficacy of Nintedanib in Special Populations (Elderly, Pregnant, and Others)

Nintedanib Efficacy and Safety in Elderly

Elderly individuals diagnosed with IPF often exhibit increased frailty, a higher prevalence of comorbidities, and a heightened susceptibility to medication side effects. Pooled data of TOMORROW, INPULSIS, and INMARK and a phase IIIb trial revealed that nintedanib significantly reduced the annual rate of decline in FVC by more than 50% at 150 mg twice daily dosage in both age groups (< 75 vs. ≥ 75 years) of patients with IPF [50]. Thus, nintedanib demonstrated consistent benefits in curtailing the progression of IPF, irrespective of patient age, particularly those aged 75 years and older [46]. A similar trend in slowing the annual FVC decline by nintedanib was observed by Komatsu et al., 2022 who suggested nintedanib as a viable option for chronic therapy in older patients with IPF [51].

Nintedanib Efficacy and Safety in Pregnancy

Nintedanib is categorized as pregnancy category D drug and is contraindicated in pregnant and breastfeeding women. It is also advised to refrain from getting pregnant while taking nintedanib and to use contraceptive measures during the treatment period. Evidence suggests nintedanib can cause damage to a developing fetus and can impact a woman's childbearing potential. Pregnancy should be avoided for at least 3 months following the last dosage of nintedanib [19].

Nintedanib Efficacy and Safety in Others

It should be noted that nintedanib is also contraindicated in patients with severe pulmonary hypertension, or hypersensitivity to nintedanib, peanut, or soya [19]. Precaution should be exercised when prescribing nintedanib to patients with higher cardiovascular risk including known coronary artery disease, hemorrhage, thromboembolic events, previous abdominal surgery, a history of aneurysm, peptic ulceration, diverticular disease or receiving concomitant corticosteroids or NSAIDs [19]. Furthermore, close monitoring is recommended in patients with low body weight (< 65 kg), Asian and female patients that have a higher risk of elevations of liver enzymes, and patients exhibiting renal impairment/failure [19].

Anti-fibrotic Agents: Current Scenario

To manage the progression of mild to moderate IPF, nintedanib and pirfenidone are the only currently approved antifibrotic therapies. In vitro assessments show a dose-dependent reduction in the proliferation of fibroblastic cells by both nintedanib and pirfenidone [52]. Various clinical trials have shown that both drugs have similar efficacy in slowing lung functional impairments and lowering the risk of hospitalization along with an improved rate of survival [7, 27]. Direct comparative data of efficacy of these two agents is extremely limited. Two real-world observational studies also confirmed the findings in terms of effectiveness and tolerability, though their study had relatively short follow-up [53, 54]. A considerable efficacy of both pirfenidone and nintedanib in terms of mitigating the decline in FVC and minimizing the risk of FVC drop of ≥ 10% predicted for 12-month period was observed in a meta-analysis conducted on ten studies [55]. There is a comparable level of long-term efficacy observed between pirfenidone and nintedanib in relation to both death rates and progression of functional illness [56]. Potentially attributable to its antiangiogenic characteristics, the use of nintedanib was seen to result in a much lesser decrease in DLCO after one year of monitoring in comparison to pirfenidone [56]. The administration of nintedanib had a substantial protective effect against the occurrence of acute exacerbation and death and showed a similar safety profile to pirfenidone [55, 56].

Compliance rates for both nintedanib and pirfenidone are reported to be comparable in the literature [57]. Both the medications reduced the number of patients with symptoms after the initial first year of treatment and these numbers reduced even further in the second year. Pirfenidone treatment reduced the number of patients with the symptoms to 47%, whereas 53% of the patients’ reported symptoms of IPF in nintedanib treatment group [57]. Progression of IPF and acute exacerbations were the most frequent reasons for discontinuation in the pirfenidone group, whereas the nintedanib treatment was discontinued due to onset of AEs [58]. There is no significant difference in patient-related outcomes such as hospitalization rate, mortality, and total as well as respiratory-related costs between the two antifibrotic medications [59]. Nintedanib treatment cessation rate before 12 months was lower, but there was an increased likelihood of acute respiratory-related hospitalizations when compared with pirfenidone, according to a real-world study from France [60]. Furthermore, a recent real-world study of Poland showed that the selection of nintedanib by pulmonary specialists was more commonly influenced by factors such as dosage protocol and patient preference, whereas the choice of pirfenidone was more frequently influenced by factors such as comorbidity profile and concomitant drug usage [61].

Nintedanib-based combination therapies for IPF disease

Combination therapies involving nintedanib and pirfenidone are currently under investigation for their efficacy and safety assessment, where preliminary findings suggest a positive outcome [62]. The in vitro study has shown pirfenidone and nintedanib combination resulting in a greater inhibition of cell growth compared to the individual agent when used separately [52].

The combined therapy of pirfenidone and nintedanib over a period of 24 weeks was shown to be associated with a comparable incidence of treatment-emergent AEs, with the prevailing occurrences being diarrhea, nausea, and vomiting, as those predicted with either monotherapy [63]. Similar results have been observed in the 12-week INJOURNEY trial [64]. Interestingly in the trial's combination treatment group, there was a higher incidence of permanent discontinuations of pirfenidone compared to permanent discontinuations of nintedanib [64]. A manageable safety and tolerability profile in patients with IPF receiving combination therapy of pirfenidone and nintedanib has been observed in a real-world study conducted in Japan [65]. The INSTAGE trial and other investigations evaluated the efficacy of nintedanib alone with different combinations, such as nintedanib plus sildenafil [66, 67]. Unfortunately, no statistically significant advantages in main outcomes were found in these investigations [66,67,68].

Safety of Nintedanib

FDA has given a list of common AEs associated with nintedanib that include diarrhea, nausea, abdominal pain, vomiting, liver enzyme elevation, decreased appetite, headache, weight decrease, and hypertension [69]. The tolerability of nintedanib is shown to be satisfactory among Indian patients diagnosed with IPF [33, 70]. Randomized trials and their open-label extension studies also suggest safety profile of nintedanib mostly marked by gastrointestinal AEs [7, 8, 64, 71, 72] which were of mild to moderate severity and were manageable [71]. Most individuals who experienced AEs related to diarrhea observed resolution of these occurrences without necessitating dosage decrease or stoppage of therapy [71]. Only 10.7% experienced a permanent reduction in dosage while 4.4% discontinued nintedanib early because of diarrhea [71]. The Indian real-world study also showed diarrhea as the prevailing AE, which was effectively controlled by reducing the dosage of nintedanib [33]. The pooled analysis of TOMORROW, INPULSIS, and INMARK trials has demonstrated nintedanib’s safety profile in patients 75 years and older to be similar to that observed in younger patients [37, 46, 51]. However, a greater percentage of older patients compared to their younger counterparts (26.4% vs. 16.0%) discontinued nintedanib due to the occurrence of AEs [37, 46].

The number of AEs associated with cardiac conditions was comparable in both nintedanib and placebo groups with myocardial infarctions being the most reported one [71]. The number of individuals experiencing ischemic heart disease was also low and comparable to placebo group [71]. Nintedanib administration is linked to AEs like increased bleeding risk, thrombosis, and thrombocytopenia. These events may be attributed to the suppression of crucial regulators of angiogenesis, i.e., FGF, PDGF, and VEGF [73]. However, nintedanib is linked with a decreased likelihood of developing cough and dyspnea in patients with IPF and ILD [74].

The safety profile of nintedanib in patients with IPF gathered from the pharmacovigilance data over a span of four years was found to be consistent with the findings outlined in global prescribing information as well as obtained in clinical trial results [75]. Notably no additional safety issues were identified during this period [75]. This empirical investigation demonstrates a 3-year survival rate of 59.4% and a minimal risk of discontinuation attributed to AEs. Real-world data indicate that the safety and tolerability profile of nintedanib remains similar in patients with IPF, regardless of the severity of their disease [32, 42].

Nintedanib is considered a well-tolerated option with better tolerability in patients intolerant against pirfenidone and switching from pirfenidone due to AEs [76, 77]. Adding nintedanib to pirfenidone has also demonstrated an acceptable safety profile [63, 64].

Long-Term Safety of Nintedanib

According to the extension study of INPULSIS® trial, nintedanib demonstrates a favorable safety and tolerability profile when used for extended period (up to 51 months and 63 months), without the emergence of any novel safety concerns [28, 72]. Nintedanib has shown promising results in decelerating the advancement of IPF for over 4 years, making it a viable treatment option for the long term [72]. The sub-group analysis of this INPULSIS®-ON study including patients with IPF of Asian race, also suggested satisfactory and sustained impact of long-term nintedanib treatment, spanning up to 64 months, consistent with shorter INPULSIS® trials [29]. On investigating the patterns of permanent cessation of nintedanib in the INPULSIS®-ON trial, it was observed that AEs occurred frequently in the first year of administration and only 11% patients discontinued nintedanib owing to AEs associated with IPF [78]. The primary cause for discontinuation of nintedanib was AEs unrelated to IPF (25.6%), followed by death (11.7%) [78]. Other reasons for nintedanib discontinuation included lung transplant and the availability of alternative commercial drugs [78].

Managing the Adverse Effects of Nintedanib Therapy

In most patients, gastrointestinal AEs related to nintedanib may resolve spontaneously. However, cases of severe diarrhea can be effectively handled by the implementation of symptomatic treatment with anti-diarrheal medicinal products such as the use of loperamide and maintenance of hydration without the necessity of reducing the dosage or interrupting therapy [19, 46]. For management of nausea and vomiting, anti-emetics can be prescribed [79]. Decreased appetite due to nintedanib can be managed with quality food, high-protein drinks, and more frequent meals while weight loss can be addressed by increasing calorie intake, eating three meals a day with snacks, and using high-protein drinks [79]. Dosage can be reduced (to 100 mg twice daily) and administered for for the long term in case of persistent AEs and increased back to normal dosage after AEs are resolved [19, 79]. Discontinuation of therapy could also be done in cases with severe AEs and may be reintroduced after these AEs subside [79, 80].

Furthermore, it is advisable to conduct regular monitoring of liver enzymes prior to and at regular intervals during the administration of nintedanib. Hepatic transaminase and bilirubin levels should be monitored within the first month of treatment, during the following two months of treatment, and at regular intervals, thereafter, as clinically indicated [19]. However, practical recommendations developed by a multidisciplinary panel of experts in 2019 states that these levels should be repeated every 4 weeks during the first 6 months of treatment, and subsequently every 3-month or as clinically indicated [46]. This practice allows for the effective management of any instances of elevated liver enzymes by appropriate measures such as dosage reduction or temporary discontinuation of treatment [71]. Also, nintedanib inhibits vascular endothelial growth factor receptor (VEGFR) that could slightly raise the risk of minor bleeding events [81]. Therefore, patients who are at high risk of bleeding, such as those with an inherited predisposition to bleeding or receiving a full dose of anticoagulant therapy, should only be given nintedanib if the anticipated advantages outweigh the possible hazards [71, 81]. The consideration of evaluation of bleeding risk and therapeutic drug monitoring is worth exploring to mitigate the potential risk of bleeding [73]. In Europe, it is further advised to regularly monitor blood pressure in patients on nintedanib, likely due to its inhibition of the VEGF pathway resulting in hypertension [81].

Various recommendations have been formulated for the treatment of patients with IPF who have cardiovascular disease (like angina, hypertension, acute coronary syndrome or valve disease), require concurrent antithrombotic medication, need surgical intervention, or are scheduled for lung transplantation [46]. Patient support programs for patient education and IPF management can potentially be advantageous in nintedanib compliance and persistence for patients with IPF. It is important to ensure that physicians in clinical practice and patients receive detailed information on early management of diarrhea. This will enable patients to comply with the prescribed medication regimen and consequently enhance the therapeutic effects of nintedanib therapy [71].

Future perspectives and Challenges

There is a challenge for healthcare professionals in determining whether they should prescribe pirfenidone over nintedanib and vice versa. The patient profiling data may help clinicians start the treatment with appropriate antifibrotic therapies in suitable patients at optimal time to increase effectiveness and ensure better prognosis. There is a need to understand these challenges in order to initiate the treatment with the right antifibrotic agents even in newly diagnosed patients with IPF.

Physician awareness of the benefits associated with antifibrotic treatment across the spectrum of IPF severity needs to be increased. Non-adherence of patients with IPF with available antifibrotic therapies is another important concern. It may lead to suboptimal disease control and poorer outcomes. Additionally, there is a lack of evidence for the treatment of subsets of patients with IPF such as IPF in extremely aged patients, with advanced fibrosis, or associated with comorbidities such as obesity, T2DM, and emphysema, which may be risk factors for disease progression.

This review addresses the efficacy and safety of nintedanib for the treatment of IPF. However, limited availability of the data related to efficacy and safety of nintedanib in pediatric population and patients suffering from multiple comorbidities is a challenge and is a limitation of the current review. Studies with sub-group analysis are needed for a more comprehensive understanding of patient profiles with these comorbidities. Furthermore, the key consideration lies in evaluating whether the benefits of the treatment outweigh any potential tolerability issues or risks, particularly in patients with comorbidities like T2DM, cardiovascular diseases, obesity, and emphysema. Thus, the risk–benefit ratio should remain a central consideration throughout this process, and the potential risks associated with untreated IPF should never be underestimated. Moreover, patient support programs aimed at providing knowledge and facilitating the management of IPF have the potential to offer benefits in terms of enhancing compliance and persistence with nintedanib therapy among patients with IPF.

Conclusions

Nintedanib, an approved anti-fibrotic drug for IPF, consistently demonstrates its role in slowing the rate of FVC decline across various patient subgroups, including those categorized by comorbidities such as obesity, T2DM, cardiovascular complications, and emphysema. Long-term safety and efficacy studies establish that nintedanib is an effective and well-tolerated treatment option for the management of IPF. This signifies its potential to impede disease progression and reduce the risk of acute exacerbations, instilling hope for those afflicted by this life-threatening condition. Gastrointestinal side effects like diarrhea and nausea are relatively common in patients undergoing nintedanib treatment. Fortunately, most of these AEs tend to be mild or moderate in intensity and can be effectively managed through vigilant side-effect monitoring, timely administration of anti-diarrheal and anti-emetic medications, lowering nintedanib dosage, and discontinuing it in case of severe symptoms with an option to reintroduce after these AEs subside. This proactive management of AEs not only results in better patient compliance and well-being but also improves overall outcomes for individuals with IPF receiving nintedanib.