Dissertation - Open Access
Doctor of Philosophy (PhD)
Breast cancer, Intraductal delivery, Lymph nodes, PLGA
Breast cancer is the second most commonly diagnosed cancer in women in the US. Ductal carcinoma in situ (DCIS) is a premalignant lesion that has not metastasized through the regional lymph nodes to other organs. Currently, all breast cancers including localized breast cancers are treated with the same aggressive therapy. Localized drug delivery by direct intraductal injections into the mammary ducts can achieve high drug concentration at the target site. However, poor retention of drugs in the ducts limits the successful translation of this approach to the clinic. To this end, the main goal of this dissertation is to develop intraductal delivery systems that can sustain drug levels in the breast and reduce the frequency of intraductal injections. The first objective was to test the influence of particle size and formulations using polystyrene (PS) particles (100-1000nm) and poly lactic-co-glycolic acid (PLGA) formulations [microspheres (MS) and in-situ gel (ISG) and nanoparticles (NP)] and to test the retention in the breast and regional lymph nodes. In vivo imaging study in rats showed that PS 1000nm was retained in the breast for 3 days compared to PS 500 nm and PS100 nm, which were retained for 2 days. The retention t ½ PS-1000nm particles was ~4-fold higher compared to 500nm, 100nm and free dye. PLGA MS and NP showed average particle size of 8.66 μm and 200 respectively. In vivo fluorescence imaging study in rats showed that PLGA ISG and MS were retained in the ducts for 4 days compared to PLGA NP and free dye, which were retained for 2 days and 4 hours respectively. The breast retention t ½ of PLGA MS and ISG was > 4-fold higher compared to PLGA NP and free dye. Furthermore, PLGA MS and NP were transported and retained in the regional lymph nodes for 48 and 24 hours respectively. PLGA formulations followed a similar biodistribution trend when tested in pig. PLGA ISG and MS were retained for 4 days and the free dye was retained only for few hours. The second objective was to develop intraductal formulations of tamoxifen (TMX) and study the in vivo biodistribution of TMX and its major active metabolites [4- hydroxytamoxifen (4HT) and endoxifen (EDX)] following intraductal delivery. The optimized PLGA MS and NP showed particle sizes of 9.12 μm and 274.1 nm respectively. In vitro release study showed that PLGA MS and ISG sustained release of TMX for > 3 weeks, while PLGA NP sustained TMX release for 2 weeks. PLGA MS and ISG T retained TMX in the breast for 2 weeks compared to PLGA NP and free TMX, which were retained 6 and 3 days respectively. The retention t ½ of TMX was delayed by >200 hours for PLGA MS and ISG compared to PLGA NP and free TMX. 4HT, a potent metabolite of TMX was generated in the mammary glands with PLGA MS and ISG and the levels were maintained above therapeutic levels for 2 weeks. No 4HT was detected in free TMX and PLGA NP groups after 2 and 7 days respectively. At the end of the treatment period (2 weeks), the amount of 4HT in the breast was 1.5 and 3.3-fold higher than free TMX group for PLGA MS and PLGA ISG respectively, and the concentration of 4HT was found to be above the therapeutic levels of 4HT in the breast. PLGA MS and ISG delayed the plasma t ½ by > 70 hours compared to free TMX. PLGA MS and ISG sustained TMX, 4HT and EDX levels in the plasma (<5ng/ml) for 2 weeks and showed ~2 fold lower systemic exposure compared to free TMX. The Cmax for free TMX was ~ 3- fold higher compared to PLGA MS and ISG. PLGA MS and ISG showed significantly lower levels of TMX, 4HT and EDX in the organs. Intraductal TMX did not show any measurable levels of TMX, EDX and 4HT in the uterus. The final objective of the dissertation was to develop and test intraductal formulations of 4HT in vivo. To further prolong drug release upto a month, a combination of 4HT loaded PLGA microspheres and in situ gel (MSG) was used. In vitro release study showed that PLGA MSG sustained 4HT release for ~1 month. MSG retained 4HT for ~1 month compared to free 4HT, which was retained only for 1 week. EDX a metabolite of 4HT was generated in the mammary glands treated with MSG. At day 28, EDX levels were 22-fold higher in MSG mammary glands compared to free 4HT. Pharmacokinetic studies in rats showed that MSG sustained 4HT and EDX levels in the plasma for 2 weeks. MSG delayed the plasma t ½ of 4HT and EDX by >3 fold compared to free 4HT. No 4HT was detected in the regional lymph nodes in the free 4HT group. On the other hand, MSG sustained therapeutic levels of 4HT in the regional lymph nodes for 14 days and was undetectable at day 28. Taken together, the findings from this dissertation demonstrate the feasibility of developing long acting intraductal formulations to prolong drug retention in the breast and reduce systemic drug distribution.
Number of Pages
South Dakota State University
In Copyright - Educational Use Permitted
Joseph, Mibin, "Long-Acting Intraductal Drug Delivery Systems for the Breast" (2019). Electronic Theses and Dissertations. 3645.
Available for download on Friday, December 18, 2020