Abaloparatide vs. Placebo in Post-Menopausal Women and Abaloparatide in Men Receiving Initial Spinal Fusion Surgery

This is a prospective randomized, double-blinded, placebo-controlled, phase 2, 12-month pilot to study the efficacy of abaloparatide in postmenopausal women needing lumbar spinal fusion surgery. Seventy-two women with low bone mass who are scheduled to undergo spinal fusion surgery will be randomized 2:1 in a blinded fashion to receive either 80 mcg of abaloparatide subcutaneously (SC) every day or an identical-appearing placebo SC for 6 months. In addition, as Tymlos is now approved for treatment in men, we will enroll 24 men aged 55 and over who will treat in an open-label design. Their responses to teriparatide will be compared to those of untreated men in an ongoing observational study, as well as to the postmenopausal women. This study has 3 objectives:

1. In this pilot study we will evaluate surgical outcomes at one year and the primary outcome will be fusion based on CT exam with categories of Fusion/ Indeterminate/ Not fused and this will be compared between groups receiving 6 months of abaloparatide vs. placebo. Secondary outcomes for surgical success will be evidence of pedicle screw loosening, adjacent segment fracture and proximal junctional kyphosis. This data will be used to determine effect sizes and variance to power the next larger clinical trial.

2. To determine if abaloparatide/Tymlos versus placebo leads to a faster reduction in pain as assessed by both the Numeric Rating Scale (NRS) and the Oswestry Disability Index (ODI) for low back pain at 6 months.

3. As an exploratory proof of concept objective we will determine if abaloparatide/Tymlos versus placebo results in greater fusion bone mass volume (FBMV) as a marker of bone union at 6 months and 1 year to see whether at one year post lumbar spinal fusion surgery, greater FBMV is associated with improved spinal surgery outcomes including: enhanced bone union, reduced pedicle screw loosening, adjacent segment fracture and proximal junctional kyphosis. This would serve as evidence that FBMV can be used as an early validated marker of fusion surgery success.

All analyses will be two-sided and the alpha level will be set at 0.05. FBMV, pain and function will be compared by drug (Abaloparatide vs. placebo) at 6 months. Compliance will be considered as taking 80% of the study drug. For the primary analysis we will evaluate bone union and reduced pedicle screw loosening, adjacent segment fracture, and proximal junctional kyphosis as dichotomous variables at 12 months using logistic regression and comparing the placebo group to the abaloparatide group. We will also evaluate FBMV as a continuous variable and evaluate differences in this outcome between abaloparatide and placebo groups at 6 months as an exploratory outcome variable. We will determine if FBMV differs in those with or without markers of surgical success for validity of FBMV, regardless of prior treatment group. In addition, these data will be used to determine effect sizes and variance to power the next larger clinical trial.

We will evaluate NRS and ODI score by using repeated measures of these variables over time by treatment group and evaluate NRS at 6 months in the placebo versus abaloparatide group. Comorbidity, age, prior fracture, prior use of bisphosphonates and other covariates will be evaluated, via multivariable regression, as to whether they lead to a change in the estimate of effect in order to be considered for inclusion in the models.

If abaloparatide can improve outcomes following lumbar spine fusion surgery, this pilot study could lead to the requisite two year trial that may have an impact on the treatment of fusion surgery patients.