Between exponential investment into AI technologies, changing global superpowers, and strategic shifts within the field, the current moment could mark a paradigm shift in drug development. Coming off the heels of a decade-long stagnation despite high R&D spending1, the urgency for innovation is heightened to rescue the trajectory of drug development.
Amongst these changing tides arises a small but powerful organism — one that has quietly undergone its own transformation to meet the challenges the industry now faces.
The Worm’s Long Trail to High-throughput Screening
The model nematode Caenorhabditis elegans has a long history in drug screening. It traces back to 1974, when late Nobel laureate Sydney Brenner published the first C. elegans-based drug screen2. Brenner tested 100 readily available compounds and found two that caused strong scorable phenotypes such as paralysis. He then selected for resistant mutants under drug pressure, revealing mutations in cholinergic pathway genes. The work showcased the genetic tractability of C. elegans and established its status as a foundational genetic model.
In 1998, C. elegans became the first animal to have its genome fully sequenced, showing that we share more in common with the simple organism than previously thought. It’s estimated that two-thirds of human genes implicated in disease have worm homologs, with many core pathways involved in development, stress, and neurodegeneration strongly conserved.
Despite this illustrious history, C. elegans was not considered a prime candidate for drug high-throughput screening (HTS), partially due to standard culture conditions that were not easily scalable. This changed in 2006, with the development of an all-liquid workflow3,4. In an early liquid culture screen, 88,000 compounds were tested for their longevity benefits. Among the 115 hits was the antidepressant Mianserin, one of the first demonstrations that a CNS drug could extend lifespan through modulation of serotonergic food-sensing pathways without decreasing food intake5.
C. elegans-based drugs screens have steadily grown over the years6, but the adoption of worms within major pharma pipelines has remained low, due to reservations about translatability and integration with more established methods. However, given the increasing uncertainty and escalating costs in drug development today, perhaps the worm deserves another look.
From Hits to Targets to Mechanisms
The process of identifying hits is inextricably linked to the underlying targets and mechanisms affected. Pharmacological innovation is slowing because we still lack strong predictive methods for identifying effective targets. As the lack of efficacy remains the primary reason for clinical trial failure7, we may have hit a plateau in finding easily druggable targets using solely in vitro assays and readouts.
Phenotypic-based approaches are increasingly being used to identify new targets and have seen success identifying first-in-class medicines8. A key advantage of C. elegans is the ability to interfere with gene function at any stage in its life cycle via RNAi delivered through feeding. This genetic tractability extends to transgenic approaches, enabling phenotypic screens for humanised disease models. In one HTS screen integrating automated imaging and analysis, compounds were screened for their ability to alter protein aggregation in transgenic worms modelling α1-antitrypsin deficiency (ATD). One hit, fluphenazine, was later shown to be effective in mammalian cell-based and mouse models with ATD9.
2D in vitro High-content screens (HCS), which prioritize multiple complex outputs over single readouts, are now routine in pharmaceutical pipelines. By capturing whole-organism responses, C. elegans addresses blind spots that even 3D organoid systems cannot resolve, improving target and biomarker predictions. As the chemical space of drug discovery diversifies into targets once thought to be undruggable10, such as transcription factors that are implicated in complex downstream pathways, whole-organism screening may become a prerequisite for capturing their systemic effects.
One Man’s Treasure is Another Man’s Treasure
C. elegans has seen considerable success in drug repurposing. The most notable case was a campaign focused on treating PMM2-CDG, a rare genetic disorder that causes neurological complications11. Epalrestat, originally used as diabetic treatment, showed a reversal of the disease phenotype in the C. elegans strain carrying the PMM2-CDG patient-specific mutation. This translated as a marked improvement of symptoms when Epalrestat was prescribed off-label to a patient, and the drug is currently in Phase III of clinical testing only five years from initial screening.
Other C. elegans repurposing screens have identified promising candidates in rare mendelian diseases, longevity,
and neurodegeneration, including a hit for ALS currently in phase II testing12. Repurposing bypasses de novo development and safety testing while extending patent life. The strategy is also about three times more likely to gain approval compared to developing new molecular entities from scratch13, making it an increasingly attractive proposition for the industry amidst record high spending and falling approval rates14,15.
The worm’s genetic tractability, in combination with its high-throughput and high-content capacity, integrates particularly powerfully into drug repurposing pipelines where the molecular targets are unclear, such as CNS disorders which experience higher late-stage failure rates than many other disease areas16. Robust hit prioritization schemes that integrate phenotypic readouts from C. elegans before committing to mouse screening are a viable strategy for reducing risk within these pipelines17.
Your Very Own Worm Avatar
Treatment options remain limited for 95% of rare diseases due to a lack of incentive and resources to develop them18. However, collectively these diseases affect more than 300 million people globally and therefore represent a gravely underserved area within medicine.
C. elegans can be engineered with patient-specific mutations using CRISPR and phenotyped systematically using high-throughput imaging. Across dozens of the Mendelian disease models available, nearly every C. elegans strain exhibits clear, quantifiable phenotypes — or can be sensitized to show one. Drug repurposing screens with these avatars identified FDA approved drugs capable of rescuing disease-associated behaviours19,20.
With the precision medicine market projected to reach ~USD 530 billion by 203521, the need for cheap and efficient platforms that can model patients-specific mutations and screen therapies in vivo will only intensify. Personalized worm assays could become a practical component of rare disease pipelines, helping translate genetic insight into actionable treatment, even for the rarest mutations.
C. elegans: Your Reliable C. ompanion
C. elegans boasts an impressive portfolio of contributions to drug development in the short time it has possessed HTS capabilities. The emerging view among researchers is that complex and diverse compounds, targets, and diseases should be met with a combination of diverse screening approaches — each leveraged for what it does best10,16. While C. elegans isn’t here to replace cell or mammalian models, it has the potential to alleviate many bottlenecks in modern drug discovery when used in combination with them. It may be time for the industry to let the worm meaningfully wiggle its way into the pipeline.
References:
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