123I-Ioflupane (DaTscan®/Striascan)

Description

¹²³I-Ioflupane, commonly known under its branded name DaTscan^® (alternatively ¹²³I-FP-CIT or ¹²³I-FPCIT, V09AB03, ¹²³I-ioflupano), is a radiopharmaceutical imaging agent developed by GE Amersham for the diagnosis of Parkinson’s disease (PD) and related conditions. First approved in the European Union on July 27, 2000, and subsequently in the United States in 2011, DaTscan^® has since played a critical role in nuclear medicine. Its initial patents entered the public domain in 2013, paving the way for generic versions.

In November 2019, Curium submitted a New Drug Application (NDA) to the U.S. FDA for a generic alternative named Striascan, securing its European marketing authorization the same year. The U.S. approval followed in late 2020, broadening the availability of ¹²³I-Ioflupane to more healthcare providers and patients.

Clinical Applications

¹²³I-Ioflupane serves as a SPECT imaging agent targeting dopamine transporters in the striatum, which are integral for evaluating dopaminergic neuronal integrity. Its clinical applications include:

1. Diagnosis of Parkinsonian Syndromes:
   • Used in adults with clinically uncertain Parkinsonian syndromes, particularly during the early stages, to distinguish essential tremors from Parkinsonian conditions such as idiopathic Parkinson’s disease, multiple system atrophy (MSA), and progressive supranuclear palsy (PSP).
   • Note: DaTscan does not differentiate among Parkinson’s disease, MSA, and PSP.
2. Differentiation of Dementia Types:
   • Helpful in distinguishing probable dementia with Lewy bodies (DLB) from Alzheimer’s disease (AD).
   • Note: DaTscan cannot differentiate between DLB and Parkinson’s disease dementia.

Significantly, the U.S. Drug Enforcement Administration (DEA) de-scheduled DaTscan in September 2015, removing its classification under the Controlled Substances Act. This regulatory change facilitated broader accessibility, ensuring that more healthcare facilities and professionals could utilize the agent. Typically, a dose of 4-5 mCi is administered in clinical settings.

Availability

Initially developed by Nycomed Amersham (now GE Healthcare), DaTscan® gained EU approval in 2000 and U.S. approval in 2011. It is marketed in South Korea and select Asian countries under the name DATrace-123 by Samyoung Unitech Co., Ltd. Curium’s generic Striascan entered the European and U.S. markets in 2019 and 2020, respectively.

A significant collaboration between ROTOP Pharmaka and Curium established a dedicated production facility in Dresden, Germany, completed by 2020. Pricing for DaTscan in the U.S. as of 2020 ranged from $2,800 to $3,000 per dose. However, increasing competition is expected to drive costs down, potentially boosting accessibility and utilization.

Competition

Despite the emergence of alternative imaging agents, DaTscan remains the dominant diagnostic tool for PD. Several precursors, such as ¹²³I-SPECTamine, ¹²³I-DopaScan, and ^99mTc-TRODAT-1, have been discontinued or are restricted to niche markets. New compounds, including ¹⁸F-DTBZ and ¹²³I-E-IACFT (Altropane), have been explored but have not achieved significant commercial presence.

The advent of PET tracers, such as ¹⁸F-FDOPA and ¹⁸F-FPCIT, offers promise for improved diagnostic accuracy. However, challenges remain in establishing large-scale adoption due to cost constraints and limited financial backing. South Korea has made strides in this area with ¹⁸F-FPCIT, but broader market penetration is pending.

Market Dynamics and Future Perspectives

The current uptake of DaTscan is not directly correlated with the prevalence of Parkinson’s disease in its markets. Barriers include the high production cost of ¹²³I-labeled compounds and the limited therapeutic benefit of confirming a PD diagnosis in the absence of definitive treatments. Additionally, while PET imaging offers superior image quality compared to SPECT, its broader adoption hinges on affordability and alignment with clinical needs.

For a competitive edge, future tracers must balance cost-effectiveness with technological innovation. Preferences will likely shift toward ¹⁸F– or ⁶⁸Ga-labeled PET agents for brain imaging due to their superior efficacy and image quality. However, challenges such as blood-brain barrier penetration may favor molecules with covalent bonds, like ¹⁸F and ¹²³I.

Outlook for Generic Versions

The introduction of generic alternatives like Striascan could revitalize interest in ¹²³I-Ioflupane by significantly lowering prices. This cost reduction may encourage widespread use in clinical practice, particularly if coupled with advances in therapeutic strategies. Moreover, the availability of generics presents an opportunity to explore broader applications of this technology in neurological diagnostics.

In conclusion, while DaTscan^® has established itself as a cornerstone in the diagnosis of Parkinsonian syndromes and related disorders, its future growth will depend on the interplay between innovation, pricing strategies, and the evolving landscape of neurotherapeutics.