Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of biotech upstarts Juno Therapeutics (NASDAQ:JUNO) and Kite Pharma (NASDAQ:KITE) both finished Monday's trading worth at least 10% less than their Friday afternoon closing prices. The two cancer treatment specialists were battered by news that pharmaceutical giant Novartis (NYSE:NVS) reported weak results for phase 1 trials of its CAR-T cellular cancer therapy.

So what: Novartis presented data at the annual American Association for Cancer Research meeting on Sunday that failed to show much success using patients' T cells to treat solid-tumor cancers. The CAR-T therapy, which modifies these cells to recognize proteins found in certain cancer cells, was safely administered but "didn't appear to have much longevity or efficacy," according to Novartis' results as reported by TheStreet biotech analyst Adam Feuerstein.

Neither Juno nor Kite presented results at the AACR meeting, but both companies are also developing solid-tumor CAR-T therapies. ZIOPHARM Oncology (NASDAQ:ZIOP), which is working on a similar treatment, also saw its shares fall by 8% after the announcement.

Now what: Biotech investors, particularly those in the oncology space, have endured many ups and downs with drug candidates that appear to be promising treatments for one type of cancer but fall short of success in treating other cancers. CAR-T treatments have seem success in treating some blood cancers, but there are more patients suffering -- and a larger commercial opportunity in treating -- solid tumor cancers. However, it's worth noting that Novartis' study was still very preliminary, and its cohort of a mere five advanced-stage patients is far too small to produce any broad-based conclusions. CAR-T may not be the right approach for solid-tumor cancers, but more research must done before it's put to rest as a viable treatment.