1. 2Invictus Oncology Pvt. Ltd. New Delhi, India
Ocular And Tissue Distribution Studies With Cabazitaxel
For Its Utility In Ocular Tumors
Rajeshkumar RK1, Bhattacharya S1, Aniruddha S2, Halder N1 and VelpandianT1
1Ocular Pharmacology & Pharmacy, Dr. R P centre, All India Institute of Medical Sciences (AIIMS), New Delhi, India
2Invictus Oncology Pvt. Ltd. New Delhi, India
Introduction
Retinoblastoma (RB) – Ocular tumor due to loss of RB gene function.
Chemotherapy failure - associated with over expression of MDR1 (P-gp transporter).
RB gene function loss - induces sensitization to taxanes as in Prostrate cancer (De Leeuw et al., 2015).
Cabazitaxel (CBZ) -Taxane derivative with less affinity for P-gp; is effective in very low concentrations (Raguz et al., 2008).
Earlier study showed the accumulation of CBZ in tumor tissue in prostrate tumor bearing mice model.
RB could be effectively treated with CBZ as it sensitizes RB protein negative cells and has low affinity for P-gp-efflux pump.
Vitreous, Plasma and Tissue samples analyzed by LC- MS/MS
LC optimized Parameters
Column:
Dr. Maisch C8, 250x4.6mm, 3.5μm, 100 A°
Mobile Phase:
ACN: Water 0.1% FA (90:10)
Objectives
Table 1: Optimized source parameters
To study ocular penetration of CBZ by quantifying it in vitreous after I.V. bolus injection.
To know the bio-distribution of CBZ in organs and plasma levels after I.V. bolus injection.
To ascertain and compare the level of clearance of CBZ between plasma and vitreous.
Source parameter
Values
Curtain gas (CUR)
20 psi
Ion spray voltage (IS)
5.5 KV
CAD 10
Temperature
450°C
GS1 and GS2
30 and 60 psi
Experimental plan
Mice 22 ± 1.8 grams divided into 2 groups (n=4).
Both groups received CBZ 5mg/kg through tail vein injection and sacrificed at 4 and 24 hrs.
Organs, plasma and vitreous collected and levels of CBZ was quantified by LC-MS/MS.
Table 2: Transitions of compounds
Conclusion
Compounds
Q1 (m/z)
Q3 (m/z)
Sulfadimithoxime (Internal Standard)
371
216
CBZ
836.6
555.3
CBZ – Na adduct
858.3
577.3
CBZ rapidly distributes into the organs within 4hrs of injection and is detectable even after 24hrs. This shows unlike tumors CBZ is not accumulating in organs.
Plasma levels at 4hrs were 159±13ng/mL; undetectable after 24 hrs.
In contrast to plasma – in vitreous CBZ reaches very less concentration after 4hrs and even after 24hrs very low concentration was detectable, this could be vitreous protein binding and poor clearance.
Compared to other organs – CBZ levels in brain, vitreous is less and this could be due to the presence of barriers.
Further in vitro and in vivo studies are in progress to asses utility of CBZ in Retinoblastoma models as it sensitizes RB protein negative cells.
CBZ extraction protocol
Tissue homogenate +
ZnCl solution
Vitreous, Plasma
Results
LLE – extraction (*MTBE)
MTBE layer – Rotovac dried
CBZ-Na
Reconstituted with extraction solvent
Calibration curve CBZ (3 to 1000ng)
Analyzed by LC- ESI-MS/MS
( positive mode)
References
* MTBE - Methyl tert-butyl ether
De Leeuw et al., Novel Actions of Next-Generation Taxanes Benefit Advanced Stages of Prostate Cancer. Clin Cancer. Res; 21(4); 795–807.
Raguz S et al., 2008.Resistance to chemotherapy: new treatments and novel insights into an old problem. British Journal of Cancer (2008) 99, 387 – 391.
Cabazitaxel
2015
Acknowledgement: Academic research grant from Invictus Oncology Pvt. Ltd. for conducting this study.