OncoSil Patent Expiry – Real Threat or Overstated Concern?

Recently, a poster highlighted the expiry of OncoSil’s core patent and implied it was a major commercial risk. I want to lay out the facts clearly — because in my view, this concern is overstated, and the reality is more complex. Let’s put it to bed.

1. The Real IP Story – It’s About a Delivery Platform, Not Just a Patent
OncoSil’s product is a targeted brachytherapy device that delivers radioactive phosphorus-32 (32P) directly into pancreatic tumours using BioSilicon™, a porous silicon delivery platform originally developed from UK defence research. The technology was first advanced commercially by pSivida Corp (now EyePoint Pharmaceuticals, NASDAQ: EYPT). The core US patent (US7060256B2 – “Therapeutic uses of bioactive porous silicon”) did expire in 2022. You can find it here: https://patents.google.com/patent/US7060256B2/en. But here's where it gets interesting: In 2012, Enigma Therapeutics (founded by Dr Roger Aston, Peter Knox, and Drew Ferguson) secured an exclusive global license to use BioSilicon for brachytherapy from pSiMedica Ltd, a subsidiary of pSivida. In 2013, Enigma was acquired by NeuroDiscovery Ltd (an ASX-listed shell) and renamed OncoSil Medical Ltd. That’s how OncoSil ended up with the exclusive global license to commercialise the technology. The patents are still owned by pSiMedica, but OncoSil holds the exclusive worldwide license — which is what matters commercially.

2. The License Is Still Valid — and May Run Until the 2030s
According to previous reports, the licensing agreement includes a clause that grants exclusivity until the later of patent expiry or ten years from the first commercial sale in a given country. Given that Europe only recently saw first commercial sales, OncoSil’s exclusivity may extend to around 2033 in some markets — regardless of the core patent expiry.
Reference: Taylor Collison Broker Report – March 2014: https://www.oncosil.com/wp-content/uploads/2022/02/2014-mar-19-taylor-collison-oncosil-research-report-wflvkhnvvemp-wfeczdzvfwox.pdf

3. Trade Secrets and Know-How Are the Real Moat
Even with patent expiry, making a competing device isn’t simple. The process of producing biocompatible, phosphorus-32-loaded porous silicon particles at medical-grade consistency — with controlled radioactivity, degradation, and safety — involves years of proprietary know-how. These are not fully disclosed in patents. They’re protected by trade secrets. So even if a competitor tried to reverse-engineer it, replicating the quality and performance would be a huge challenge.

4. What Would a Competitor (Like Sirtex) Need to Do?
Let’s be generous and say a company like Sirtex wanted to enter this space. They’d need to: reverse engineer the product, develop a biosimilar device with matching safety and efficacy data, build or repurpose facilities to handle and package radioactive phosphorus-32, run independent clinical trials, navigate regulatory approvals (EU MDR, FDA HDE or PMA), establish surgeon training and hospital trust, and secure reimbursement codes. Even in an optimistic scenario, it’s 4–6 years and US$10–20 million, with no guaranteed path to market.

5. Surgeons and Hospitals Don’t Switch Easily
Here’s the thing most people overlook: clinicians are conservative by nature, especially with implantable radioactive devices. It takes time to: train surgical teams, build confidence in outcomes, align with hospital purchasing pathways, and satisfy medico-legal and radiation safety protocols. Even if a “biosimilar” device appeared, hospitals would be slow to adopt unless it had substantial evidence and cost advantages. The switching cost is real, and OncoSil has already done the hard yards.

6. Don’t Forget the Complexity of Radiopharmaceuticals
This isn’t like copying a simple medical device. Working with radioactive isotopes like phosphorus-32 adds a serious layer of complexity: it requires specialised handling licences, involves tight regulatory oversight for manufacturing, transport, and disposal, and comes with higher operating costs and institutional barriers. Only a handful of companies globally are set up to manage this kind of therapeutic product — and OncoSil is one of them.

7. OncoSil’s Future IP Strategy – Enter OncoCal™
To strengthen their long-term commercial protection, OncoSil is already planning beyond the BioSilicon platform. They are developing OncoCal™, a calcium-based delivery system to replace silicon, offering several strategic advantages:

• Outright ownership – OncoCal™ would be royalty-free and no longer dependent on pSiMedica.

• Patent filings are already underway, with expected coverage through 2032 (without extensions).

• This protects OncoSil’s future products under its own patent portfolio, giving them more control and flexibility.

So while the current OncoSil™ product is licensed under patents owned by pSiMedica, OncoSil Medical is actively building its next-generation IP moat through OncoCal™, aiming for stronger commercial independence and patent protection.

Final Take
Yes, the core patent expired. But this isn’t a free-for-all.

• OncoSil holds an exclusive global license, still likely valid in key markets.
• Trade secrets and manufacturing know-how make copying difficult.
• Regulatory and clinical barriers are high.
• Surgeon trust and adoption don’t flip overnight.
• Handling radioactive material isn’t something you spin up in a warehouse.
• Next-gen OncoCal™ platform adds further IP strength through 2032.

In short: the moat is wider than it looks. Patent expiry is worth noting — but it’s not a commercial death sentence, and in my view, the threat is largely theoretical.

Happy to be corrected if anyone has a real-world example of a competitor successfully entering a market like this post-patent expiry — especially one involving radioactive materials and implantable devices. Always open to learning more if there’s something I’ve missed.