**Cost Analysis for Mirabegron Use in the Treatment of Children with Neurogenic Bladder**

**Rena Xu, MD, MBA**, Andrea Balthazar, MD, MPH, Mihail Samnaliev, PhD, Rebecca Sherlock, PNP, Carlos R. Estrada, Jr., MD, MBA.

Boston Children's Hospital, Boston, MA, USA.

**Background:** Mirabegron, a beta-3 adrenergic receptor agonist, received FDA approval in 2021 to treat neurogenic detrusor overactivity in children ages three years and older. Despite studies demonstrating its safety and efficacy, access to mirabegron is often restricted by payor coverage policies that require trial of several other treatments first. This cost-analysis study sought to determine the cost implications from a payor perspective of mirabegron use at different points in the treatment pathway for pediatric neurogenic bladder.**Methods: **A Markov decision analytic model was used to assess the expected costs over a 10-year time horizon (20 six-month cycles) for eight hypothetical treatment strategies (**Table 1**). Strategies A and B entail sequential use of three anticholinergic medications (oxybutynin, tolterodine, and solifenacin or trospium), followed by onabotulinum toxin type A (Botox) injection and augmentation cystoplasty. Strategies C-G incorporate mirabegron use at different points in the treatment pathway; Strategy H entails first-line Botox. Model inputs were obtained from clinical literature on the efficacy, side effect profiles, attrition rates, and costs associated with each treatment option; transition probabilities between strategies were based on published treatment efficacy and adverse event rates and adjusted to a 6-month cycle. Costs were adjusted to 2021-dollar value. A discount rate of 3% was used. To quantify uncertainty, costs and treatment transition probabilities were modeled as gamma and beta distributions, respectively, and probabilistic sensitivity analysis (PSA) was conducted using a Monte Carlo simulation with 100,000 iterations. Analyses were performed using Treeage Pro (Healthcare Version).**Results: **The expected cost of Strategy A, the "base case," was $58,689 (Table 1). Strategy C, involving first-line mirabegron use, was the least costly ($38,173). Strategies D-G, the other strategies involving mirabegron use, were all less costly than the base case. On PSA, the probability of being the least costly pathway was 83% for Strategy C (mean $37,577, 95% CI: $37,545-37,608), 0.5% for Strategy E (mean $38,588, 95% CI: $38,555-38,620), 1% for Strategy F (mean $38,759, 95% CI: $38,727-38,791), and 15.5% for Strategy G (mean $39,025, 95% CI: $38,993-39,057). Cost savings associated with mirabegron use were driven by decreased use of augmentation cystoplasty and Botox injections, which accounted for $33,731 in costs in Strategy A as compared to $12,977 in Strategies C-G (**Figure 1**).**Conclusions:** This is the first study to compare costs across multiple strategies involving mirabegron to treat pediatric neurogenic bladder. Using mirabegron likely yields cost savings for the payor: the least costly strategy involved first-line mirabegron, and all pathways incorporating mirabegron were less costly than the base case. These findings, combined with evidence of mirabegron's safety and efficacy, suggest that expansion of payor coverage for mirabegron should be considered. The findings also suggest an opportunity for further clinical studies to investigate first-line mirabegron use.

Strategy name | Treatment pathway sequence | Expected cost (Incremental cost from reference) |

A."Base case" (Reference) | 1. Oxybutynin 2. Add tolterodine 3. Switch tolterodine to solifenacin 4. Add botox 5. Augmentation cystoplasty | $58,689 |

B."Base case with trospium" (Trospium as third-line) | 1. Oxybutynin 2. Add tolterodine 3. Switch tolterodine to trospium 4. Add botox 5. Augmentation cystoplasty | $79,562 ($20,873) |

C."First-line mirabegron switch" (Mirabegron, then switch to base case) | 1. Mirabegron 2. Switch mirabegron to oxybutynin 3. Add tolterodine 4. Switch tolterodine to solifenacin 5. Add botox 6. Augmentation cystoplasty | $38,173 (-$20,516) |

D."First-line mirabegron additive" (Mirabegron, then add to base case) | 1. Mirabegron 2. Add oxybutynin 3. Switch mirabegron to tolterodine 4. Switch tolterodine to solifenacin 5. Add botox 6. Augmentation cystoplasty | $42,624 (-$16,065) |

E."Second-line mirabegron" (Insert mirabegron into base case as second-line) | 1. Oxybutynin 2. Add mirabegron 3. Switch mirabegron to tolterodine 4. Switch tolterodine to solifenacin 5. Add botox 6. Augmentation cystoplasty | $39,253 (-$19,436) |

F."Third-line mirabegron" (Insert mirabegron into base case as third-line) | 1. Oxybutynin 2. Add tolterodine 3. Switch tolterodine to mirabegron 4. Switch mirabegron to solifenacin 5. Add botox 6. Augmentation cystoplasty | $39,415 (-$19,274) |

G."Fourth-line mirabegron" (Insert mirabegron into base case as fourth-line) | 1. Oxybutynin 2. Add tolterodine 3. Switch tolterodine to solifenacin 4. Switch solifenacin to mirabegron 5. Add botox 6. Augmentation cystoplasty | $39,666 (-$19,023) |

H.First-line Botox (Rearrange order of base case) | 1. Botox 2. Switch botox to oxybutynin 3. Add tolterodine 4. Switch tolterodine to solifenacin 5. Augmentation cystoplasty | $71,939 ($13,250) |

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