The first patient has been treated with CytomX Therapeutics‘ investigational Probody drug conjugate CX-2009 in a new phase 1/2 clinical trial. The drug candidate is designed to target a surface molecule found in a number of solid tumors, including castration-resistant prostate cancer.
Developed by CytomX, Probody therapeutics are engineered to bind selectively to cancer cells and not healthy cells to reduce toxicity while remaining effective at fighting malignant tumors.
To achieve this level of specificity, the technology takes advantage of the presence of tumor-released enzymes that have the capacity to cleave a small protein that masks the drug target binding site. Because these enzymes are found only in the tumor microenvironment, the drug’s binding site can only act close to cancer cells.
“The unique targeting ability of our Probody platform allows us to pursue targets not accessible to conventional antibody drug conjugates,” Sean McCarthy, D.Phil, president and CEO of CytomX Therapeutics, said in a press release.
CX-2009 specifically targets the CD166 protein that is highly expressed on the cell surface of several types of solid tumors, including prostate, breast, and endometrial cancers.
The investigational drug combines the Probody technology with a toxic compound called maytansine DM4. After binding to CD166 on the surface of cancer cells, CX-2009 is internalized into the cells and releases the toxin, triggering cell death.
“With CX-2009, we are leveraging the high levels of CD-166 on many types of cancer cells despite its presence on normal tissue,” McCarthy said.
“By targeting CD-166 and localizing the activity of the CX-2009 Probody therapeutic to the tumor, we could potentially treat a number of cancers for which few, if any, treatment options exist,” he added.
The PROCLAIM-CX-2009 trial (NCT03149549) is currently recruiting participants. It is expected to enroll about 150 patients with select cancer types, including non-small cell lung cancer, castration-resistant prostate cancer, breast cancer, ovarian cancer, endometrial cancer, head and neck cancer, and cholangiocarcinoma (cancer of the bile ducts).
The trial’s primary goal is to determine an effective and safe doseof CX-2009 to be used as a stand-alone, anti-cancer therapy. CX-2009’s safety profile and overall response rate to treatment are the primary and secondary outcome measures to be assessed during the trial.