Extrapolation of Survival Data Using a Bayesian Approach: A Case Study Leveraging External Data from Cilta-Cel Therapy in Multiple Myeloma

INTRODUCTION

Extrapolating long-term overall survival (OS) from shorter-term clinical trial data is key to health technology assessment in oncology. However, extrapolation using conventional methods is often subject to uncertainty. Using ciltacabtagene autoleucel (cilta-cel), a chimeric antigen receptor T-cell therapy for multiple myeloma, we used a flexible Bayesian approach to demonstrate use of external longer-term data to reduce the uncertainty in long-term extrapolation.

METHODS

The pivotal CARTITUDE-1 trial (NCT03548207) provided the primary efficacy data for cilta-cel, including a 12-month median follow-up snapshot of OS. Longer-term (48-month median follow-up) survival data from the phase I LEGEND-2 study (NCT03090659) were also available. Twelve-month CARTITUDE-1 OS data were extrapolated in two ways: (1) conventional survival models with standard parametric distributions (uninformed), and (2) Bayesian survival models whose shape prior was informed from 48-month LEGEND-2 data. For validation, extrapolations from 12-month CARTITUDE-1 data were compared with observed 28-month CARTITUDE-1 data.

RESULTS

Extrapolations of the 12-month CARTITUDE-1 data using conventional uninformed parametric models were highly variable. Using informative priors from the 48-month LEGEND-2 dataset, the ranges of projected OS at different timepoints were consistently narrower. Area differences between the extrapolation curves and the 28-month CARTITUDE-1 data were generally lower in informed Bayesian models, except for the uninformed log-normal model, which had the lowest difference.

CONCLUSIONS

Informed Bayesian survival models reduced variation of long-term projections and provided similar projections as the uninformed log-normal model. Bayesian models generated a narrower and more plausible range of OS projections from 12-month data that aligned with observed 28-month data.

TRIAL REGISTRATION

CARTITUDE-1 ClinicalTrials.gov identifier, NCT03548207. LEGEND-2 ClinicalTrials.gov identifier, NCT03090659, registered retrospectively on 27 March 2017, and ChiCTR-ONH-17012285.

Component Costs of CAR-T Therapy in Addition to Treatment Acquisition Costs in Patients with Multiple Myeloma

INTRODUCTION

Ciltacabtagene autoleucel (cilta-cel), is a B-cell maturation antigen-directed, genetically modified autologous chimeric antigen receptor T-cell (CAR-T) immunotherapy. It is indicated for treatment for adult patients with relapsed or refractory multiple myeloma (RRMM) after four or more prior lines of therapy, including a proteasome inhibitor, an immunomodulatory agent, and an anti-CD38 monoclonal antibody. The objective of this study was to estimate the per-patient US commercial healthcare costs related to cilta-cel (CARVYKTI^®) CAR-T therapy (i.e., costs separate from cilta-cel therapy acquisition) for patients with RRMM.

METHODS

US prescribing information for cilta-cel, publicly available data, and published literature were used with clinician input to identify the cost components and unit costs associated with administration of cilta-cel. Cost components included apheresis, bridging therapy, conditioning therapy, administration, and postinfusion monitoring for 1 year of follow-up. Adverse event (AE) management costs for all grades of cytokine release syndrome and neurologic toxicities, and additional AEs grade ≥ 3 occurring in > 5% of patients were included in the analysis.

RESULTS

The estimated per-patient average costs of cilta-cel CAR-T therapy administered exclusively in an inpatient setting, excluding cilta-cel therapy acquisition costs, totaled US$160,933 over a 12 month period. Costs assuming different proportions of inpatient/outpatient administration (85%/15% and 70%/30%) were US$158,095 and US$155,257, respectively.

CONCLUSION

Cost estimates from this analysis, which disaggregates CAR-T therapy costs, provide a comprehensive view of the cost components of CAR-T therapy that can help healthcare decision-makers make informed choices regarding the use of cilta-cel. Real-world costs may differ with improved AE prevention and mitigation strategies.

The Burden of X-Linked Retinitis Pigmentosa on Patients and Society: A Narrative Literature Review

X-linked retinitis pigmentosa (XLRP) is a severe form of retinitis pigmentosa (RP), a rare, inherited retinal degenerative disorder, that causes blindness. The aim of this literature review was to identify what is currently known about the burden of XLRP. Literature databases were searched for articles describing the clinical, humanistic, or economic burden of XLRP or RP in the US, Japan, France, Germany, Italy, Spain, and the UK, published in English between 2014 and 2019; gray literature and cited references were reviewed. Literature describing XLRP is limited as this is an ultra-rare condition; findings relating to burden of RP have been reported with interpretation of how burden differs for XLRP. In XLRP, night blindness usually presents in the first decade of life, followed by loss of peripheral and then central vision; legal blindness is reported at a median of 45 years in affected males (vs median 70 years for RP). There is limited evidence of humanistic or economic burden specific to XLRP; one study identified greater vision-related activity limitations in patients with XLRP compared with the wider RP population. Qualitative studies describe increased humanistic burden for people living with RP; difficulty undertaking everyday tasks (driving, hobbies, reading), psychosocial burden and barriers to work and career. People described the emotional impact of dealing with progression of RP, ongoing social and physical challenges, and the impact of RP on relationships. The economic burden of RP is associated with lost productivity, greater healthcare costs and increasing requirement for formal and informal care. In summary, XLRP remains an untreatable condition that can impact people from childhood. The humanistic burden of RP has been shown to increase as the disease progresses; hence, in XLRP the earlier onset and earlier progression to blindness during prime working years may mean a comparatively greater lifetime burden of disease.

Optic nerve gliomas. II. Cytological characteristics. Observations on cell and tissue cultures

Cytological characteristics of optic nerve gliomas were studied parallel with histological structures in cell and tissue cultures. Histologically the tumours consisted of four different cell types: spindle-shaped elongated cells, round cells, stellate forms, and multinucleated cells. Dynamic properties of cultured optic glioma cells showed that stable cellular elements of the parent tissue arise from two fundamental populations, viz from elongated (piloid), and from round cells. Cells of both populations displayed a series of changes in the course of their cultures. A certain part of the slender elongated cells enlarged and became plump piloid cells of various shapes, or big stellate astrocytes. Giant multinucleated variants of these forms also emerged by fusion of the mononucleate forms. The round cells gradually turned into immature Astrocytes, and by a subsequent cell fusion they gave birth to big stellate cells. With the ageing of the cultures a polymorphous cellular picture developed which was mainly due to the active migratory and intracellular movement of the elongated and round cellular elements. Mitoses played a negligible role in this process. Several characteristics suggest that the round shapes are immature glia cells, and represent the least differentiated elements among all the cell components. The stellate and giant multinucleated forms might be considered as end-products of glia cell differentiation and they could originate both from the elongated and the round cells.