Abstract P6-21-12: Local transdermal therapy (LTT): Drug permeation and distribution of telapristone acetate (TPA) in a pre-surgical window study of women undergoing mastectomy

Background: Low uptake and poor adherence to oral drugs for breast cancer prevention and ductal carcinoma in situ has led to an interest in local routes of delivery with the intent of decreasing systemic exposure and reducing toxicity. LTT has emerged as a possible alternative; previous studies have shown selectively higher concentrations in the breast than in the serum with this delivery route. A question related to LTT is whether or not the drug will permeate and distribute throughout the breast, as is expected with oral delivery.

Methods: We conducted a double-blind study of oral versus LTT delivery of the selective progesterone receptor modulator, telapristone acetate (TPA), in a presurgical window setting, enrolling 82 women planning therapeutic or prophylactic mastectomy. We randomized 67 women 1:1, to oral TPA 12 mg daily, or gel TPA applied to both breasts daily (12 mg/breast), for 4 weeks ±1 week. Mastectomy specimens were sampled at 5 non-tumor locations as well as the tumor and lymph node when available. Samples were split in two: drug concentration (conc.) assay using LC-MS/MS and histological evaluation of tissue composition (fat, fibrous stroma, epithelium). The primary endpoint was mean drug conc. across all breast locations (anticipating that the gel would deliver a mean concentration that was >50% of the mean in the oral group). A secondary endpoint was the drug distribution pattern across the breast, expecting that the distribution would be similar. The tumor sample was saved for biomarker assays related to TPA action; these are ongoing, for a pre-planned pooled analysis of data with NCT01800422 (reported in SABCS abstract 851863).

Results: Of 63 evaluable women (33 oral and 30 gel group), 27 had unilateral and 36 had bilateral mastectomy. The mean drug conc. in the oral group was 166.3 ng/G (SE 11.7), and in the gel group was 10.6 ng/G (SE 10.8), (p<.0001). The conc. was variable across the 7 locations tested in both groups. High concentrations were found in the superficial and deep central locations, retroareolar and lateral locations ranked in the middle, and the medial location was discrepant, being high in the oral and low in the gel group. The variation in drug concentration across all locations was not significantly different between groups (Kolmogorov-Smirnov p=0.99). Among women with bilateral mastectomy, drug concentrations were similar between breasts in both oral and gel groups. In the gel group, despite low TPA concentrations, there was evidence of drug metabolism. The major metabolite, CDB 4453 was detectable in 192/193 samples with detectable parent drug. Analysis of drug concentration adjusted for tissue composition is ongoing.

Conclusions: The gel formulation of TPA did not permeate the skin well. However, the drug delivered to the breast was distributed throughout the breast, similar to the oral delivery route, with the highest concentration in the deep central location. These drug distribution data are novel; drug distribution at multiple locations throughout the breast has not previously been shown. Further work is needed to understand breast distribution with formulations known to have good dermal permeation.

Citation Format: Lee O, Pilewskie M, Xu Y, Benante K, Blanco L, Helenowski I, Tull MB, Muzzio M, Jovanovic B, Karlan S, Hansen N, Bethke K, Kulkarni S, Perloff M, Dimond EP, Heckman-Stoddard BM, Khan SA. Local transdermal therapy (LTT): Drug permeation and distribution of telapristone acetate (TPA) in a pre-surgical window study of women undergoing mastectomy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-21-12.

Abstract OT1-04-01: A phase IIB pre-surgical trial of oral tamoxifen (TAM) versus transdermal 4-hydroxytamoxifen (4-OHT) in women with DCIS of the breast

Background

Ductal carcinoma in situ (DCIS) is diagnosed in 60,000 women annually in the US. TAM is proven to reduce risk of local recurrence and new primary breast cancer in women with estrogen receptor (ER) positive DCIS. However, acceptance of TAM has been low, primarily because of toxicity related to systemic exposure. Local delivery to the breast is an attractive alternative since low systemic levels could minimize toxicity. 4-OHT is an active metabolite of TAM. When formulated as a gel and applied to the breast skin, it is well tolerated, and results in 4-OHT breast tissue drug levels comparable oral TAM. In small pilot studies, its anti-proliferative effects on invasive breast tumors and DCIS are also similar to oral TAM [Lee O, et al. PMID 25028506]. The goal of our study is to validate these results in preparation for a Phase III trial of 4-OHT gel in comparison to oral TAM.

Methods

We are conducting a randomized, double-blinded, placebo-controlled, Phase IIB pre-surgical trial to demonstrate that daily application of 4-OHT gel will result in a reduction in the Ki-67 labeling index of DCIS lesions that is not inferior to that seen in women receiving daily oral TAM 20 mg daily. Ki-67 of the base-line diagnostic core needle biopsy will be compared to that of the therapeutic surgical excision sample after oral TAM or 4-OHT gel for 8 ± 2 weeks. Secondary endpoints include changes in Oncotype DCIS-Score, IHC markers (CD68, COX2, p16), hormone levels, coagulation markers, drug concentration in the plasma and breast tissue, the fraction of women with no residual DCIS in the surgical sample, and experienced symptoms. 100 women (assuming 20% non-evaluable samples or compliance issues) with DCIS (10% ER-positive) will be enrolled across six institutions into two intervention arms: oral TAM 20 mg daily, placebo gel and 4-OHT gel 4mg daily (2mg/breast), placebo capsule. All participants will be evaluable for toxicity from their first dose. All samples from all participants who receive drug will be evaluated and included in the primary analysis, which will be based on intent to treat principle. To date 15 of 100 participants have been enrolled across six institutions including: Northwestern University in Chicago, IL, St. Elizabeth Healthcare in Edgewood, KY, Duke University Medical Center in Durham, NC, Cleveland Clinic in Cleveland, OH, Memorial Sloan Kettering Cancer Center in New York, NY, and Mayo Clinic in Rochester, MN. Since study open, 69 potential participants have been contacted, 52 did not consent for screening, 17consented for screening, 2 are pending consent, and 15 have started study intervention. The most common reasons potential participants chose not to consent are wanting to schedule surgery as soon as possible, attitudes toward medical research, and current use of a prohibited concomitant medication such as a potent inhibitor of tamoxifen metabolism or exogenous sex steroid.

Funding Source: NCI Contract # HHSN2612201200035I.

Citation Format: Benante KA, Xu Y, Tull MB, Segura AJ, Alber KM, Kalinichenko K, Hou L, Jovanovic B, Perloff M, Heckman-Stoddard B, Dimond E, Khan SA. A phase IIB pre-surgical trial of oral tamoxifen (TAM) versus transdermal 4-hydroxytamoxifen (4-OHT) in women with DCIS of the breast [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT1-04-01.