Shares of Juno Therapeutics (JUNO) and Kite Pharma (KITE) are weak Monday following a lackluster showing for so-called CAR-T cellular therapies in solid tumors at a closely watched cancer conference this weekend. 

T cells taken from patients and modified by scientists at the University of Pennsylvania and Novartis (NVS) - Get Report to recognize a protein found on some solid-tumor cancers could administered safely but didn't appear to have much longevity or efficacy, according to research presented Sunday at the American Association for Cancer Research (AACR) annual meeting. The new data were not altogether surprising but disappointed investors who expecting more progress for CAR-T in solid tumors. To date, all of the excitement surrounding CAR-T has come from very high remission rates in patients with advanced blood cancers, a smaller commercial market.

Juno Therapeutics fell 6% to $60.70 in early Monday trading. Kite is down 7% to $60.79. Neither company presented data at the AACR meeting this weekend but their stocks fell because they also have solid tumor CAR-Ts in development. Ziopharm Oncology (ZIOP) - Get Report  and Bellicum Pharmaceuticals (BLCM) - Get Report, two more CAR-T stocks, were also trading lower Monday.

As reported Sunday, the phase I study was conducted using a CAR-T therapy from Novartis and the University of Pennsylvania. T cells were taken out of patients and modified with receptors to identify a protein known as mesothelin expressed on the surface of certain tumors. The modified T cells, now able to detect and kill mesothelin-containing tumors, were then grown and reinfused back into the patients. The new immunotherapy, known as CART-meso (short for mesothelin), was administered to five patients with advanced cancers no longer responding to multiple lines of prior therapy. Two patients had ovarian cancer, two had epithelial mesothelioma (a type of lung cancer) and one patient had pancreatic cancer.

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.