TY  - CONF
AU  - Topalović, Igor A.
AU  - Marković, Olivera S.
AU  - Pešić, Miloš P.
AU  - Kathawala, Mufaddal
AU  - Serajuddin, Abu T. M.
AU  - Avdeef, Alex
AU  - Verbić, Tatjana
PY  - 2023
UR  - http://cherry.chem.bg.ac.rs/handle/123456789/5994
AB  - Methods for drug solubilization have become important part of modern drug discovery and 
development due to increasing number of extremely insoluble drugs and drug candidates. 
One of such methods is acid-base supersolubilization (ABS) [1]. Clofazimine (CFZ) is weakly 
basic antibiotic and anti-inflammatory drug, most notably used in the treatment of leprosy
and tuberculosis, with recently proven inhibitory activity against several coronaviruses [2].
We have recently unraveled its aqueous pKa value and its unique cosolvent dependence [3]. 
The aim of the present study was to investigate CFZ solubilization using the ABS approach. 
Eight small organic acids were tested for the ABS effect (glutaric, malic, tartaric, citric, 
malonic, maleic, succinic, adipic) but only glutaric (GA), malic (MA), and tartaric (TA) acids 
showed some solubilization effect. The effect of their concentration (and the solution pH 
value) was further tested. The solubility of CFZ was determined in GA, MA, and TA solutions 
in wide concentration (1.0×10-2 – 5.0 M) and pH range (~0.2 – 4.8). Equilibration time was 
24 hours (6 h of stirring + 18 h of sedimentation). Phases were separated by filtration. The 
CFZ concentration in supernatant was determined by HPLC-UV/VIS. Results show that CFZ 
solubility increases as acid concentration increases: from 3.04×10-3 to 10.68 mg/mL (in GA), 
from 9.06×10-3 to 1.23 mg/mL (in MA) and from 4.76×10-3 to 0.32 mg/mL (in TA). The effect 
of CFZ solubilization is much more pronounced when the acid concentration is raised above 
2 M. These results can be used as the basis for further CFZ formulation optimization.
Furthermore, our ongoing research is focused on the type of interactions and other possible 
factors that can influence CFZ and other prectically insoluble drugs, embracing (super)solu bilization as a general methodology in drug design and development.
PB  - International Association of Physical Chemists
C3  - 10th IAPC Meeting: Tenth World Conference on Physico-Chemical Methods in Drug Discovery & Sixth World Conference on ADMET and DMPK Belgrade, Serbia, September 4-6, 2023
T1  - Clofazimine acid-base solubilization: influence  of small organic acids’ concentration
SP  - 66
EP  - 66
UR  - https://hdl.handle.net/21.15107/rcub_cherry_5994
ER  - 

@conference{
author = "Topalović, Igor A. and Marković, Olivera S. and Pešić, Miloš P. and Kathawala, Mufaddal and Serajuddin, Abu T. M. and Avdeef, Alex and Verbić, Tatjana",
year = "2023",
abstract = "Methods for drug solubilization have become important part of modern drug discovery and 
development due to increasing number of extremely insoluble drugs and drug candidates. 
One of such methods is acid-base supersolubilization (ABS) [1]. Clofazimine (CFZ) is weakly 
basic antibiotic and anti-inflammatory drug, most notably used in the treatment of leprosy
and tuberculosis, with recently proven inhibitory activity against several coronaviruses [2].
We have recently unraveled its aqueous pKa value and its unique cosolvent dependence [3]. 
The aim of the present study was to investigate CFZ solubilization using the ABS approach. 
Eight small organic acids were tested for the ABS effect (glutaric, malic, tartaric, citric, 
malonic, maleic, succinic, adipic) but only glutaric (GA), malic (MA), and tartaric (TA) acids 
showed some solubilization effect. The effect of their concentration (and the solution pH 
value) was further tested. The solubility of CFZ was determined in GA, MA, and TA solutions 
in wide concentration (1.0×10-2 – 5.0 M) and pH range (~0.2 – 4.8). Equilibration time was 
24 hours (6 h of stirring + 18 h of sedimentation). Phases were separated by filtration. The 
CFZ concentration in supernatant was determined by HPLC-UV/VIS. Results show that CFZ 
solubility increases as acid concentration increases: from 3.04×10-3 to 10.68 mg/mL (in GA), 
from 9.06×10-3 to 1.23 mg/mL (in MA) and from 4.76×10-3 to 0.32 mg/mL (in TA). The effect 
of CFZ solubilization is much more pronounced when the acid concentration is raised above 
2 M. These results can be used as the basis for further CFZ formulation optimization.
Furthermore, our ongoing research is focused on the type of interactions and other possible 
factors that can influence CFZ and other prectically insoluble drugs, embracing (super)solu bilization as a general methodology in drug design and development.",
publisher = "International Association of Physical Chemists",
journal = "10th IAPC Meeting: Tenth World Conference on Physico-Chemical Methods in Drug Discovery & Sixth World Conference on ADMET and DMPK Belgrade, Serbia, September 4-6, 2023",
title = "Clofazimine acid-base solubilization: influence  of small organic acids’ concentration",
pages = "66-66",
url = "https://hdl.handle.net/21.15107/rcub_cherry_5994"
}

Topalović, I. A., Marković, O. S., Pešić, M. P., Kathawala, M., Serajuddin, A. T. M., Avdeef, A.,& Verbić, T.. (2023). Clofazimine acid-base solubilization: influence  of small organic acids’ concentration. in 10th IAPC Meeting: Tenth World Conference on Physico-Chemical Methods in Drug Discovery & Sixth World Conference on ADMET and DMPK Belgrade, Serbia, September 4-6, 2023
International Association of Physical Chemists., 66-66.
https://hdl.handle.net/21.15107/rcub_cherry_5994

Topalović IA, Marković OS, Pešić MP, Kathawala M, Serajuddin ATM, Avdeef A, Verbić T. Clofazimine acid-base solubilization: influence  of small organic acids’ concentration. in 10th IAPC Meeting: Tenth World Conference on Physico-Chemical Methods in Drug Discovery & Sixth World Conference on ADMET and DMPK Belgrade, Serbia, September 4-6, 2023. 2023;:66-66.
https://hdl.handle.net/21.15107/rcub_cherry_5994 .

Topalović, Igor A., Marković, Olivera S., Pešić, Miloš P., Kathawala, Mufaddal, Serajuddin, Abu T. M., Avdeef, Alex, Verbić, Tatjana, "Clofazimine acid-base solubilization: influence  of small organic acids’ concentration" in 10th IAPC Meeting: Tenth World Conference on Physico-Chemical Methods in Drug Discovery & Sixth World Conference on ADMET and DMPK Belgrade, Serbia, September 4-6, 2023 (2023):66-66,
https://hdl.handle.net/21.15107/rcub_cherry_5994 .

TY  - JOUR
AU  - Marković, Olivera S.
AU  - Pešić, Miloš P.
AU  - Shah, Ankita V.
AU  - Serajuddin, Abu T.M.
AU  - Verbić, Tatjana
AU  - Avdeef, Alex
PY  - 2019
UR  - https://cherry.chem.bg.ac.rs/handle/123456789/2924
AB  - Although solubility-pH data for desipramine hydrochloride (DsHCl) have been reported previously, the aim of the present study was to critically examine the aqueous solubility-pH behavior of DsHCl in buffer-free and buffered solutions, in the presence of physiologically-relevant chloride concentration, using experimental practices recommended in the recently-published “white paper” (Avdeef et al., 2016). The computer program pDISOL-X was used to design the structured experiments (pH-RSF method), to process the data, and to refine the equilibrium constants. Low-to-high and high-to-low pH assays (using HCl, H 3 PO 4 , or NaOH to adjust pH) were performed on phosphate-buffered (0.12‑0.15 M) saturated solutions of DsHCl in the pH 1.3–11.6 range. After equilibration (stirring 6 h, followed by 18 h stir-free sedimentation), filtration or centrifugation was used for phase separation. Concentration was measured using HPLC with UV/VIS detection. The 2:1 drug-phosphate solubility product (K sp 2:1 = [DsH + ] 2 [HPO 4 2− ]) was determined from data in the pH 4–9 region. The free base of desipramine was prepared and used to determine the K sp 1:1 ([DsH + ][H 2 PO 4 − ]) in chloride-free acidified suspension. In addition, phosphate-free titrations were conducted to determine the intrinsic solubility, S 0 , and the 1:1 drug-chloride solubility product, K sp DsH [rad] Cl = [DsH + ][Cl − ]. Under the assay conditions, only the phosphate-free solutions showed some supersaturation near pH max 8.0. In phosphate-containing solutions, pH max was indicated at higher pH (8.8–9.6). Oils mixed with solids were observed to form in alkaline solutions (pH > 11). Notably, soluble drug-phosphate complexes appeared to form below pH 3.9 and above pH max in saturated phosphate‑containing saline solutions. This was indicated by the systematic pH shift to higher values in the log S-pH curve in alkaline solution than expected from the Henderson-Hasselbalch equation. For pH < 3.9, saturated phosphate-containing saline solutions exhibited elevated solubility, with drug-hydrochloride as the sole precipitate. Salt solubility products, intrinsic solubility, and complexation constants, which rationalized the data, were determined. Elemental, thermogravimetric (TGA), differential scanning calorimetric (DSC), and powder X-ray diffraction (PXRD) analyses were used to characterize the precipitates isolated from suspensions at different pH.
PB  - Elsevier
T2  - European Journal of Pharmaceutical Sciences
T1  - Solubility-pH profile of desipramine hydrochloride in saline phosphate buffer: Enhanced solubility due to drug-buffer aggregates
VL  - 133
SP  - 264
EP  - 274
DO  - 10.1016/j.ejps.2019.03.014
ER  - 

@article{
author = "Marković, Olivera S. and Pešić, Miloš P. and Shah, Ankita V. and Serajuddin, Abu T.M. and Verbić, Tatjana and Avdeef, Alex",
year = "2019",
abstract = "Although solubility-pH data for desipramine hydrochloride (DsHCl) have been reported previously, the aim of the present study was to critically examine the aqueous solubility-pH behavior of DsHCl in buffer-free and buffered solutions, in the presence of physiologically-relevant chloride concentration, using experimental practices recommended in the recently-published “white paper” (Avdeef et al., 2016). The computer program pDISOL-X was used to design the structured experiments (pH-RSF method), to process the data, and to refine the equilibrium constants. Low-to-high and high-to-low pH assays (using HCl, H 3 PO 4 , or NaOH to adjust pH) were performed on phosphate-buffered (0.12‑0.15 M) saturated solutions of DsHCl in the pH 1.3–11.6 range. After equilibration (stirring 6 h, followed by 18 h stir-free sedimentation), filtration or centrifugation was used for phase separation. Concentration was measured using HPLC with UV/VIS detection. The 2:1 drug-phosphate solubility product (K sp 2:1 = [DsH + ] 2 [HPO 4 2− ]) was determined from data in the pH 4–9 region. The free base of desipramine was prepared and used to determine the K sp 1:1 ([DsH + ][H 2 PO 4 − ]) in chloride-free acidified suspension. In addition, phosphate-free titrations were conducted to determine the intrinsic solubility, S 0 , and the 1:1 drug-chloride solubility product, K sp DsH [rad] Cl = [DsH + ][Cl − ]. Under the assay conditions, only the phosphate-free solutions showed some supersaturation near pH max 8.0. In phosphate-containing solutions, pH max was indicated at higher pH (8.8–9.6). Oils mixed with solids were observed to form in alkaline solutions (pH > 11). Notably, soluble drug-phosphate complexes appeared to form below pH 3.9 and above pH max in saturated phosphate‑containing saline solutions. This was indicated by the systematic pH shift to higher values in the log S-pH curve in alkaline solution than expected from the Henderson-Hasselbalch equation. For pH < 3.9, saturated phosphate-containing saline solutions exhibited elevated solubility, with drug-hydrochloride as the sole precipitate. Salt solubility products, intrinsic solubility, and complexation constants, which rationalized the data, were determined. Elemental, thermogravimetric (TGA), differential scanning calorimetric (DSC), and powder X-ray diffraction (PXRD) analyses were used to characterize the precipitates isolated from suspensions at different pH.",
publisher = "Elsevier",
journal = "European Journal of Pharmaceutical Sciences",
title = "Solubility-pH profile of desipramine hydrochloride in saline phosphate buffer: Enhanced solubility due to drug-buffer aggregates",
volume = "133",
pages = "264-274",
doi = "10.1016/j.ejps.2019.03.014"
}

Marković, O. S., Pešić, M. P., Shah, A. V., Serajuddin, A. T.M., Verbić, T.,& Avdeef, A.. (2019). Solubility-pH profile of desipramine hydrochloride in saline phosphate buffer: Enhanced solubility due to drug-buffer aggregates. in European Journal of Pharmaceutical Sciences
Elsevier., 133, 264-274.
https://doi.org/10.1016/j.ejps.2019.03.014

Marković OS, Pešić MP, Shah AV, Serajuddin AT, Verbić T, Avdeef A. Solubility-pH profile of desipramine hydrochloride in saline phosphate buffer: Enhanced solubility due to drug-buffer aggregates. in European Journal of Pharmaceutical Sciences. 2019;133:264-274.
doi:10.1016/j.ejps.2019.03.014 .

Marković, Olivera S., Pešić, Miloš P., Shah, Ankita V., Serajuddin, Abu T.M., Verbić, Tatjana, Avdeef, Alex, "Solubility-pH profile of desipramine hydrochloride in saline phosphate buffer: Enhanced solubility due to drug-buffer aggregates" in European Journal of Pharmaceutical Sciences, 133 (2019):264-274,
https://doi.org/10.1016/j.ejps.2019.03.014 . .