Background: Sacubitril/valsartan, marketed as Azmarda (manufactured by the innovator company) is a cocrystal consisting 6 sacubitril and valsartan molecules, along with sodium cations and water molecules. This formulation is considered a major mechanism of benefit of this molecule. This study was aimed to assess various brands of sacubitril/valsartan in the market for the presence of the cocrystal forms and compare them with Azmarda. a brand of sacubitril/valsartan manufactured by the innovator company.
Methods: The study involved analysis of various marketed products containing sacubitril/valsartan tablets, including Azmarda. Both the Azmarda and marketed products were characterized using differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). Sodium content and dissolution studies were also performed .
Results: A total of 16 brands of marketed products including Azmarda were studied. During DSC studies, unique melting pattern was observed in Azmarda, with exothermic peaks of sacubitril/valsartan detected at 140°C and 102°C, respectively. PXRD analysis revealed that none of the products exhibited the same crystal lattice as Azmarda. Azmarda, with a sodium level of 1.773%, was comparable to brand 2 (1.61%), brand 4 (1.73%), and brand 7 (1.58%). Azmarda demonstrated 64% release of sacubitril and 57% release of valsartan within 30 minutes in 0.1N HCl. Brand 7, brand 12, and brand 13 showed 52%, 57%, and 52% release of sacubitril, respectively, and 45%, 52%, and 48% release of valsartan, respectively, in 30 minutes.
Conclusion: The absence of identical crystal lattice structures, highlights absence of co-crystals in generic formulations. Such variations may impact the bioavailability and efficacy, emphasizing the importance of ensuring consistent and reliable therapeutic outcomes.
Sacubitril/valsartan represents a pioneering class of medications, combining neprilysin inhibition with angiotensin II receptor antagonism. This unique combination effectively enhances endogenous natriuretic peptides while inhibiting the renin–angiotensin-aldosterone system [1]. Sacubitril/valsartan is a cocrystal consisting of 6 sacubitril and 6 valsartan moieties in their anionic forms, 18 penta- and hexa-coordinated sodium cations, and 15 water molecules.
According to the PARADIGM-HF trial findings, sacubitril/valsartan demonstrated a significant advantage over enalapril in reducing cardiovascular mortality, heart failure hospitalization risk, heart failure symptoms, and physical limitations. The trial was prematurely stopped after a median follow-up of 27 months, revealing substantial advantages of sacubitril/valsartan [2]. The TRANSITION study further demonstrated the feasibility of achieving target doses within 10 weeks. This study revealed that initiating sacubitril/valsartan stabilized patients with heart failure with reduced ejection fraction (HFrEF) following an acute heart failure event, whether in the hospital or shortly after discharge [3].
Valsartan, classified as a Biopharmaceutical Classification System (BCS) Class II, exhibits low solubility and high permeability [4]. This classification suggests that bioavailability from oral dosage forms is dissolution rate limited. Sacubitril/valsartan are highly hygroscopic in nature and difficult to handle when used in amorphous (non-crystalline) form and can adversely affect it invitro and in vivo performance including storage concerns. A drug's efficacy depends on various factors, including solubility, stability, dissolution rate, and hygroscopicity [5]. Ongoing research explores methods to enhance oral absorption for medications with low water solubility and/or limited permeability, with pharmaceutical cocrystals emerging as a promising tool for improving bioavailability [6].
Study design and material
The study involved the analysis of various marketed products containing sacubitril/valsartan tablets, including Azmarda manufactured by innovator company. The sacubitril/valsartan sodium salt complex in cocrystal form was acquired from Ami Life Sciences. Solid-state forms were identified using X-ray powder diffraction. The solvents and reagents used for co-crystallization, such as isopropyl alcohol, hydrochloric acid (HCl), sodium phosphate buffer, sodium hydroxide, nitric acid, and hydrogen peroxide, were of analytical grade from Merck Limited. Double-distilled water or high-performance liquid chromatography (HPLC) grade water was used as needed.
Physical mixture preparation method
Sacubitril/valsartan were mixed in a defined 1:1 stoichiometric ratio. This mixture was prepared and carefully stored away from light and moisture.
Differential Scanning Technology (DSC)
The thermal behaviour of the cocrystal was determined using the Perkin Elmer Model STA-8000 with DSC. Before measurement, the instrument was calibrated for temperature and heat flow using standard indium. A weighted sample (5 mg) was placed in a sealed non-hermetic aluminium pan, and a hold time of 1 minute at 45°C was maintained. The measurement was then conducted with an increasing step size of 10°C/min under a dry nitrogen atmosphere, running the sample from 45°C to 235°C. Subsequently, the peaks were estimated, and the resulting data were analyzed using the simultaneous thermal analyzer DSC from PerkinElmer.
Powder X-ray diffraction (PXRD)
The distinct peak of each compound was characterized using PXRD. Subsequently, various brands of marketed products in India were assessed against Azmarda tablets to investigate the presence of the innovative cocrystal in the formulation. All samples, within an uncertainty range of (5 mg - 20g), were weighed using an analytical balance (Mettler Toledo). The product underwent powder X-ray diffraction (PXRD) analysis, with samples exposed to Cu Kα radiation (0.15405 nm) at a tube voltage of 40 kV and a current of 30 mA. Data were collected within the 2θ range of 2° to 49.721°, employing a step size of 0.031 under atmospheric pressure. For sample preparation, the required quantity was taken into a mortar, and a fine powder was gently obtained using a pestle. The powdered sample was then placed on the sample holder, packed, and the surface was smoothed with a microscopic slide.
Sodium content determination
Sodium content was determined using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES; Agilent 5110 Instrument) for the sacubitril/valsartan sodium complex, Azmarda, and sacubitril/valsartan tablets. Sodium content of different marketed products of sacubitril/valsartan tablets was measured with parameters including radio frequency (RF) power ranging from 750W to 950W, atomizer airshed set at 1.00 to 1.25 L/min, assisted gas flow between 0.5 to 1.00 L/min, and a vertical observation height of 15 to 18 mm.
For sample preparation, 1.0 g of the sample was transferred into a 100.0 mL Teflon/PTFE vessel, followed by the addition of 1.0 mL of hydrogen peroxide and 10.0 mL of concentrated nitric acid. The Teflon/polytetrafluoroethylene (PTFE) vessel was then placed in a microwave digestion apparatus. After cooling the mixture to room temperature, the plasma was ignited and allowed to stabilize for approximately 15 minutes. The blank solution was aspirated, and the signal was zeroed. In triplicate cycles, the diluent, standard, and sample solutions were aspirated into the plasma, and the ionization intensity of different elements was measured.
Dissolution studies
The dissolution studies were conducted in 900 mL of 0.1N HCl and pH 6.8 phosphate buffers using a USP Type II dissolution apparatus (Lab India DS 14000 SMART) with a paddle speed set at 75 rpm. Various marketed products of sacubitril/valsartan tablets were subjected to dissolution studies. The temperature of the dissolution medium was maintained at 37°C ± 0.5°C throughout the specified time limit. Tablet samples of marketed products were subjected to the dissolution study. The 10 mL sample aliquots were collected at 15, 30, 45 min time points from the dissolution vessel and same were replaced with an equal volume of fresh medium. The sample aliquot solution was then filtered through a 0.45 μ polyvinylidene difluoride (PVDF) filter (Make: Millipore) for analysis at 242 nm using the HPLC.
A total of 16 brands of marketed product of sacubitril/valsartan tablets, including Azmarda were studied in the present analysis.
The DSC thermograms of marketed products was determined for 11 brands including Azmarda indicating exothermic peaks for sacubitril/valsartan between 131°C and 165°C and 72°C and 114°C, respectively (Table 1, Figure 1). A distinct melting pattern was observed in the reference product, with exothermic peaks of sacubitril/valsartan detected at 140°C and 102°C, respectively.
The PXRD analysis revealed that none of the products exhibited the same crystal lattice as Azmarda tablets. The prominent peaks of Azmarda were observed at position of 2θ, specifically at 4.125, 5.267, 12.482, and 22.496 (Figure 2 and 3). Among other comparators, brand-9 showed three peaks around 2θ value of 4.082, 5.047 and 12.420. Brand 5, 8, 11, 13 and 14 showed two peaks around 2θ value 4 and 5; brand 12 showed two peaks around 2θ value of 4.391 and 5.917; brand 2, 4, 7 and 10 showed two peaks around 2θ value of 4 and 22; however, brand 3, 15 and 16 showed only peak around 2θ value of 4. The prominent peaks of Azmarda in PXRD pattern confirmed the crystalline nature of compound; as compared to all other brands.
Sodium content was determined for 11 brands including Azmarda. Analysis showed that Azmarda had a sodium level of 1.72%, which was comparable to the sodium levels in brand 2 (1.61%), brand 4 (1.73%), and brand 7 (1.58%) (Figure 4). Other marketed products had a higher sodium level ranging from 3.164 to 3.951.
The innovator product, Azmarda, based on cocrystal technology, demonstrated a 64% release of sacubitril and a 57% release of valsartan within 30 minutes in 0.1N HCl (Table 2, Figure 5 and 6). Marketed products such as brand 7, brand 12, and brand 13 showed 52%, 57%, and 52% release of sacubitril respectively, and 45%, 52%, and 48% release of valsartan,
respectively, in 30 minutes. Most of the marketed products exhibited very negligible drug release in 0.1N HCl. Similarly, within 45 minutes there was 68% release of sacubitril and 61% release of valsartan which was much higher than all other products. Sacubitril/valsartan are freely soluble in pH 6.8 phosphate buffer and complete drug release is observed in 30 minutes during dissolution study in pH 6.8 phosphate buffer (Table 3).
Table 1: Results of DSC data of sacubitril/valsartan tablets of marketed products
Brand name |
Melting point of sacubitril 133°C-136°C exotherm observed on temperature (°C) |
Melting point of valsartan 80°C-95°C exotherm observed on temperature (°C) |
Brand 1 (Azmarda) |
140 |
102 |
Brand 2 |
130 |
85 |
Brand 3 |
134-163 |
72-113 |
Brand 4 |
138 |
75 |
Brand 5 |
137 |
101 |
Brand 6 |
137 |
101 |
Brand 7 |
131 |
90 |
Brand 8 |
140 |
103 |
Brand 9 |
140 |
110 |
Brand 10 |
134-165 |
75-114 |
Brand 11 |
134-165 |
81-102 |
Table 2: Dissolution data of marketed products in 0.1N HCl
Sacubitril/valsartan tablets 50 mg dissolution with 0.1N HCl |
||||||
Brand name |
% Release |
|||||
15 min |
30 min |
45 min |
||||
Sacubitril |
Valsartan |
Sacubitril |
Valsartan |
Sacubitril |
Valsartan |
|
Brand 1 (Azmarda) |
52 |
46 |
64 |
57 |
68 |
61 |
Brand 2 |
15 |
15 |
31 |
29 |
39 |
37 |
Brand 3 |
6 |
6 |
8 |
7 |
9 |
8 |
Brand 4 |
3 |
3 |
7 |
6 |
9 |
8 |
Brand 5 |
1 |
1 |
1 |
1 |
1 |
1 |
Brand 6 |
1 |
1 |
2 |
2 |
3 |
4 |
Brand 7 |
39 |
33 |
52 |
45 |
64 |
55 |
Brand 8 |
5 |
5 |
7 |
6 |
15 |
13 |
Brand 9 |
7 |
8 |
9 |
9 |
10 |
11 |
Brand 10 |
2 |
1 |
16 |
6 |
5 |
4 |
Brand 11 |
1 |
1 |
2 |
2 |
3 |
3 |
Brand 12 |
53 |
49 |
57 |
52 |
61 |
57 |
Brand 13 |
42 |
39 |
52 |
48 |
59 |
54 |
Brand 14 |
1 |
1 |
2 |
2 |
3 |
3 |
Brand 15 |
8 |
8 |
12 |
13 |
15 |
16 |
Brand 16 |
2 |
2 |
3 |
2 |
3 |
3 |
Table 3: Dissolution data of marketed products in pH 6.8 phosphate Buffer
Sacubitril/valsartan tablets 50 mg dissolution results with pH 6.8 phosphate buffer |
||||||||||
Brand name |
% Release |
|||||||||
5 min |
10 min |
15 min |
30 min |
45 min |
||||||
Sacubitril |
Valsartan |
Sacubitril |
Valsartan |
Sacubitril |
Valsartan |
Sacubitril |
Valsartan |
Sacubitril |
Valsartan |
|
Brand 1 (Azmarda) |
50 |
50 |
88 |
88 |
102 |
101 |
100 |
99 |
98 |
97 |
Brand 2 |
30 |
35 |
62 |
70 |
84 |
93 |
95 |
105 |
93 |
103 |
Brand 3 |
59 |
61 |
95 |
98 |
102 |
102 |
99 |
101 |
99 |
101 |
Brand 4 |
10 |
10 |
53 |
54 |
98 |
100 |
101 |
103 |
99 |
100 |
Brand 5 |
35 |
35 |
76 |
75 |
99 |
98 |
100 |
100 |
98 |
97 |
Brand 6 |
52 |
52 |
88 |
87 |
103 |
103 |
95 |
94 |
96 |
95 |
Brand 7 |
45 |
48 |
85 |
88 |
100 |
99 |
98 |
99 |
97 |
100 |
Brand 8 |
39 |
39 |
90 |
88 |
103 |
101 |
102 |
100 |
100 |
98 |
Brand 9 |
60 |
61 |
97 |
98 |
103 |
103 |
102 |
102 |
103 |
103 |
Brand 10 |
44 |
44 |
80 |
80 |
97 |
95 |
98 |
98 |
100 |
98 |
Brand 11 |
58 |
59 |
96 |
97 |
102 |
104 |
99 |
100 |
100 |
100 |
Brand 12 |
78 |
81 |
98 |
103 |
101 |
102 |
97 |
101 |
99 |
103 |
Brand 13 |
50 |
51 |
91 |
91 |
102 |
102 |
100 |
99 |
100 |
100 |
Brand 14 |
54 |
53 |
93 |
92 |
102 |
102 |
98 |
97 |
99 |
97 |
Brand 15 |
58 |
60 |
92 |
94 |
100 |
102 |
96 |
98 |
95 |
97 |
Brand 16 |
67 |
68 |
100 |
101 |
102 |
103 |
100 |
101 |
101 |
102 |
Figure 2. Powder X-ray diffraction profile of sacubitril/valsartan
Figure 3. The characteristics powder diffraction peaks are described in terms of 2θ values for different marketed samples