How I can help your business

• Provide strategic IP advice across all areas of chemistry, with particular expertise in pharmaceuticals (small molecules and antibody-drug conjugates), agrochemicals and genetic sequencing
• Coordinate international patent prosecution and portfolio strategy to support consistent, commercially aligned protection across jurisdictions
• Draft patent applications to protect your key innovations and commercial interests

Overview & Expertise

Jian Siang is a Senior Associate and UK Chartered and European Patent Attorney at Marks & Clerk’s London office. He works with a wide range of clients on drafting, prosecuting and handling worldwide patent portfolios, particularly in relation to new chemical entities including small molecules and antibody-drug conjugates, as well as genetic sequencing methods.

He has experience in prosecuting applications relating to polymers, light-emitting devices, medical devices and semiconductors. His practice also includes advising on freedom to operate, due diligence and validity matters in the pharmaceutical and agrochemical fields, as well as handling EPO opposition proceedings for both patentees and opponents.

Jian Siang holds a PhD in Synthetic Organic Chemistry from the University of Cambridge, where part of his research focused on developing new flow chemical methodologies in collaboration with agrochemical and pharmaceutical companies. He also holds a first class MSci degree in Natural Sciences (Chemistry) from the University of Cambridge.

He was named a “Rising Star” by Managing Intellectual Property in 2025 and was awarded the Chris Gibson prize for achieving the highest overall mark in one of the UK patent qualification examinations.

Client Work & Case Experience

• Pharmaceutical and life sciences sector — managing global patent portfolios and prosecuting applications relating to small molecules and antibody-drug conjugates.
• Cross-sector technologies — prosecuting applications relating to agrochemicals, polymers, medical devices, genetic sequencing, semiconductors and light-emitting devices.
• EPO proceedings — representing both patentees and opponents in opposition matters.