Girod, C

Abstract Rationale Lymphangioleiomyomatosis (LAM) is a rare, progressive, cystic lung disease affecting women. Sirolimus has been shown to stabilize lung function in women with LAM, but real-world data on long-term safety and efficacy are limited. Methods The NIH Multicenter Safety and Durability of Sirolimus for LAM (MIDAS, NCT02432560) observational registry was launched in 2015. All adult (≥18 years) women with LAM (treated or untreated) were eligible to enroll at any of the 20 U.S. sites and followed longitudinally with serial assessments of lung function, health-related quality of life, and treatment related adverse event (TRAEs). Baseline cohort characteristics and TRAEs are summarized using descriptive analyses. Marginal structural models (MSMs) with inverse probability of treatment weighting estimated the causal effect of sirolimus on annualized forced expiratory volume in one-second (FEV1) decline, adjusting for age at LAM diagnosis, prior treatment with sirolimus, menopausal status, race, presence of angiomyolipomas, supplemental oxygen use; time-varying covariates included diffusing capacity for carbon monoxide (DLCO) and serum vascular endothelial growth factor-D (VEGF-D) levels. Results Longitudinal data was available in 350 LAM patients, most of whom (246, 70.3%) had sporadic LAM. The median age at the baseline pulmonary function test (PFT) measurement was 46 years (range: 19 - 74) and the median (IQR) number of serial PFTs obtained per patient was 3 (1 - 5). The average follow-up duration per patient was 2.8 years. Over half of the patients (196, 56%) were treated with sirolimus during the MIDAS observation period for a median (IQR) treatment duration of 4.9 (2.4 - 7.5) years. MSM analysis demonstrated that sirolimus treatment was durably effective and reduced FEV₁ decline by 74.36 mL/year (95% CI: 15.87 - 132.85) compared with no treatment (-85.31 mL/year for the untreated group vs. -10.95 mL/year for the treated group, p = 0.01). Sirolimus was generally well tolerated; treatment interruption ≥3 months was observed in 38 (19.4%) of the 196 sirolimus treated patients. Logistic regression analysis showed that higher levels of FEV1 (odds ratio: OR = 3.12 [1.45 - 7.11], p = 0.005), VEGF-D (OR = 1.0007 [1.0004 - 1.001], p < 0.001), and DLCO (OR = 1.023 [1.0053 - 1.0413, p = 0.01]), were associated with treatment interruption. Conclusions In the MIDAS cohort, sirolimus treatment resulted in durable stabilization of lung function with a favorable safety profile over a 5-year period. These real-world data support sirolimus as a chronic suppressive therapy for LAM, demonstrating durable efficacy in slowing lung disease progression and tolerability with long-term use. This abstract is funded by: National Institutes of Health

Abstract Background: Lymphangioleiomyomatosis (LAM) is a rare, female-predominant, low-grade neoplasm that can lead to progressive diffuse cystic lung disease. Pregnancy has been associated with accelerated disease progression and increased risk of spontaneous pneumothoraces in women with LAM. Sirolimus is the current first line treatment for LAM and has demonstrated benefit in stabilizing lung function decline and reducing the risk of spontaneous pneumothoraces; however, there is unclear evidence regarding the risk benefit ratio of the use of sirolimus during pregnancy. Methods: We queried physicians across the LAM Clinic Network and obtained information regarding demographics, baseline characteristics, LAM related complications, lung function, sirolimus dosing, and pregnancy outcomes in women with LAM who took sirolimus during pregnancy. Results: We identified 9 women with LAM who had used sirolimus during pregnancy for a total of 12 pregnancies. All women had sporadic LAM with moderate lung function impairment prior to pregnancy: median FEV1 56% predicted, median DLCO 43% predicted, and 2 patients on supplemental oxygen. Sirolimus was used throughout pregnancy in most instances (10/12 (83.3%)). Sirolimus was held prior to pregnancy in 2 patients; both these patients experienced a spontaneous pneumothorax in the first trimester and resumed sirolimus in the second trimester with no further pneumothoraces during the rest of the pregnancy. The median sirolimus dose during pregnancy was 1 (range 1-2) mg daily with a median trough level of 2.95 (range: 1 – 6.7) ng/ml. Ten pregnancies (83.3%) resulted in live births, 1 pregnancy was terminated due to molar pregnancy, and 1 pregnancy resulted in miscarriage. Spirometry and DLCO were available in 8 pregnancies and tended to be stable (Figure 1). None of the 10 pregnancies that resulted in live births reported any fetal health issues. Seven out of these 10 children (70%) were breastfed with continued sirolimus use. At the time of submission of this report, the median age of these children is 3.5 years (range: 1 – 6.5 years) with no reported adverse health outcomes from sirolimus exposure during pregnancy. Conclusions: The use of sirolimus during pregnancy in women with LAM appears to be safe for both mother and fetus and might help reduce the pregnancy associated risks of accelerated lung function decline and spontaneous pneumothoraces.