Sanofi snaps up Synthorx for $2.5bn, eyeing cancer immunotherapy combinations


Sanofi has agreed to buy cancer drugs firm Synthorx for around $2.5 billion, aiming to strengthen its immune-oncology drug pipeline and creating the possibility of new combination therapies.

The giant French pharma said it will pay $68 per share in cash for the clinical stage biotech.

While Sanofi’s pipeline is stuffed full of trials and candidates for inflammatory diseases and multiple sclerosis, Sanofi is also developing Libtayo (cemiplimab), a PD-1 checkpoint inhibitor class drug targeting diseases such as non-small cell lung cancer and cervical cancer and already approved in the skin cancer metastatic cutaneous squamous cell carcinoma.

This seems to be the rationale for the acquisition, as Sanofi said that Synthorx’s drugs seem to work both in combination with this form of immunotherapy, as well as on their own.

Based in San Diego, Synthorx has a lead product candidate, THOR-707, a variant of interleukin-2 that is in clinical development for several solid tumour types as a single agent and in combination with immune checkpoint inhibitors.

Sanofi thinks it could become the best IL-2 therapeutic for treatment of solid tumours, after showing improved pharmacology, less frequent dosing, and therapeutic superiority compared with other IL-2 compounds.

As Sanofi’s release suggests, there is nothing new about IL-2 therapy, which has been available for more than 20 years in diseases such as metastatic kidney cancer and metastatic melanoma.

But pharma companies are looking at combinations that could improve response rates and efficacy for checkpoint inhibitors after the initial success of PD-1 class drugs such as Merck & Co’s Keytruda and Bristol-Myers Squibb’s Opdivo.

According to Sanofi, IL-2 could become a “foundation” for future combinations involving two immune-oncology combination therapies.

THOR-707 and related compounds from Synthorx could be combined with Sanofi’s clinical and pre-clinical oncology assets.

Sanofi is also developing isatuximab in cancer indications such as multiple myeloma, where it is under review.

THOR-707 could also work in combination with CD-38 targeting drugs such as isatuximab, as well as molecules that modulate effector T-cells and natural killer cells, Sanofi said.