Biotech investors got their first look at clinical trial data to be presented at the American Society for Clinical Oncology (ASCO) meeting when abstracts were released a few weeks ago. But companies had to turn in their abstracts back in February, so the outcomes for ongoing clinical trials are long out of date, leading to the potential for stock-moving readouts at the meeting itself.

It's impossible to preview the entire meeting, but looking through the program, here are two major themes investors should be watching as ASCO kicks off on Friday:

1. CAR Ts

The Food and Drug Administration approved the first two chimeric antigen receptor T-cell (CAR T) therapies -- Novartis' (NYSE:NVS) Kymriah and Gilead Sciences' (NASDAQ:GILD) Yescarta -- last year. But there are plenty more in the pipeline, and we may even hear updated data on the first-generation drugs.

On Friday evening, bluebird bio (NASDAQ:BLUE) and Celgene (NASDAQ:CELG) will kick things off with their BCMA-targeted CAR T, bb2121, for patients with multiple myeloma who have failed other treatments. The results from the phase I trial have been impressive so far, albeit in a limited number of patients. The new data should include the expansion cohort of patient treated at the dose to be used in later-stage trials.

Blood vials on a diagnostic test request

Image source: Getty Images.

Gilead is scheduled to present a readout of the durability of response for Yescarta as it continues to follow patients in the ZUMA-1 trial that got the therapy approved. But investors should also be looking ahead to Saturday, when Gilead will present data from ZUMA-3, a trial in patients with acute lymphoblastic leukemia treated with KTE-C19, which has the same targeting construct as Yescarta but is manufactured under a slightly different process.

In an interesting head-to-head trial, researchers in China tested the co-stimulatory signaling domains used in Kymriah and Yescarta in patients with B-cell acute lymphoblastic leukemia. In the initial results disclosed in the abstract, Kymriah's co-stimulatory signaling domain appeared to be slightly better, although with the small number of patients, it's hard to make a firm conclusion. The update at ASCO could provide more details.

Finally, Celgene will present updated results for JCAR017 in patients with non-Hodgkin lymphoma who have failed other therapies, which will be crucial for justifying its $9 billion purchase of Juno Therapeutics.

Doctor showing patient a report in a hospital bed

Image source: Getty Images.

2. PD-1 combinations

Programmed death 1 (PD-1) receptor and its ligand, PD-L1, come together to inhibit the immune cells from attacking tumor cells. Drugs that interrupt that interaction, such as Bristol-Myers Squibb's (NYSE:BMY) Opdivo and Merck's (NYSE:MRK) Keytruda, work well, except in cases where immune cells aren't in the tumor, leading many companies to develop combinations that seek to directly or indirectly increase the activity of immune cells and thus the efficacy of PD-1/PD-L1 drugs.

Perhaps the most anticipated of the group is Nektar Therapeutics(NASDAQ:NKTR) NKTR-214 that Bristol-Myers Squibb (NYSE:BMY) licensed earlier this year, which binds to CD122 to stimulate cancer-killing T cells and natural killer cells. Interim data in the abstract for the phase 1/2 PIVOT trial testing NKTR-214 plus Bristol-Myers' Opdivo were a little disappointing, but the updated ASCO presentation on Saturday could help alleviate investors' fears of falling response rates.

Exelixis (NASDAQ:EXEL) and Bristol-Myers continue their love-hate relationship with results from a trial testing Exelixis' Cabometyx and Opdivo in patients with urothelial carcinoma. The duo are already testing the combination in a phase 3 trial called CheckMate 9ER, so investors are looking for this updated data to give them confidence that the combination is continuing to work.

Technician looks at mammogram results on a computer

Image source: Getty Images.

The phase 2 TOPACIO/Keynote-162 trial tests Tesaro's (NASDAQ:TSRO) poly (ADP-ribose) polymerase (PARP) inhibitor, Zejula, with Keytruda. On Sunday, outcomes for patients with recurrent ovarian cancer will be presented, as Tesaro and Merck look to build on earlier promising results. Then on Monday, the duo will present data testing the combination in patients with metastatic triple-negative breast cancer as Tesaro looks to expand the market for Zejula.

Finally -- at least for this article, as there are certainly other combinations that investors could be watching -- Jounce Therapeutics (NASDAQ:JNCE) will present results from the Iconic trial testing JTX-2011 with and without Opdivo in patients with advanced cancers, as the biotech and its partner Celgene look to bounce back from disappointing data presented in the initial abstract.

Data overload?

Check back to The Motley Fool over the weekend and into Monday as we take a closer look at the results presented at ASCO.

Brian Orelli has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Bluebird Bio, Celgene, Exelixis, and Gilead Sciences. The Motley Fool has a disclosure policy.