We devise a new method to produce smooth estimates of baseline survival and hazard functions for incomplete data observed subject to interval‐censoring, that can in principle be viewed as being nonparametric. The key idea is to start from the nonparametric maximum likelihood estimate, and to then construct an empirical moment generating function for the underlying data generating mechanism, which is subsequently inverted via a saddlepoint approximation in order to obtain smooth distributional estimates. Unlike the typical spline‐based and other semiparametric methods that have thus far been devised for the same purpose, the proposed approach is unencumbered by the choice of tuning parameters. Simulation studies show that in terms of integrated squared error, the method is very close in performance to the parametric gold standard, and should generally be preferred over the well‐established spline‐based approach implemented in R package logspline. The methodology is illustrated on some publicly available real datasets, and its implications and limitations are discussed.

TPS5111 Background: Darolutamide is a structurally distinct and highly potent androgen receptor inhibitor with low blood–brain barrier penetration. In the phase 3 ARAMIS study (NCT02200614) of patients with nonmetastatic castration-resistant prostate cancer, treatment with darolutamide significantly improved metastasis-free survival and overall survival versus placebo, with a favorable safety profile. The incidences of central nervous system adverse events (AEs; e.g. falls, memory impairment, and depression) showed a ≤2% difference between the darolutamide and placebo groups. Fatigue was the only AE with an incidence of > 10% for darolutamide (13.2% vs 8.3% for placebo). In a separate neuroimaging study of healthy volunteers, cerebral blood flow was not altered in patients treated with darolutamide but was significantly reduced in brain areas related to cognition in patients treated with enzalutamide. Furthermore, it is postulated that the low blood–brain barrier penetration of darolutamide may result in lower serum testosterone elevations than those seen with enzalutamide, with the potential of leading to fewer associated feminizing AEs. The objective of ARAMON (NCT05526248) is to compare the effect of darolutamide and enzalutamide monotherapy on post-treatment testosterone levels in patients with hormone-naive prostate cancer experiencing biochemical recurrence after definitive treatment for localized disease. Methods: ARAMON is a two-stage, open-label, phase 2 study of patients with histologically or cytologically confirmed adenocarcinoma of the prostate who have biochemical recurrence after radical primary prostatectomy or radiation therapy, with a prostate-specific antigen (PSA) doubling time of ≤20 months, baseline serum testosterone > 150 ng/dL, and Eastern Cooperative Oncology Group performance status 0/1. During a 52-week lead-in phase, 25 patients will receive darolutamide 600 mg twice daily. If criteria based on serum testosterone increase from baseline to Week 12 are met, the study will proceed to a 52-week randomized phase in which the effects of darolutamide (600 mg twice daily, n = 20) will be compared with the effects of enzalutamide (160 mg once daily, n = 20). The primary endpoint of both phases is the change in serum testosterone level from baseline to Week 12. Secondary endpoints of the randomized phase include the change in serum testosterone levels from baseline to Weeks 24 and 52; PSA at Weeks 4, 12, 24, 36, and 52; changes in blood levels of markers for glucose, lipid metabolism, and endocrine function related to sex hormones; safety; and quality of life. Safety will be assessed through AE monitoring. The first of the 25 planned patients in the lead-in phase was enrolled on January 13, 2023. Clinical trial information: NCT05526248 .