Cardiff Oncology has reported updated results from its phase 2 colorectal cancer trial, laying out data it believes can support talks with the FDA about a registrational program. Investors, though, responded by sending the biotech’s share price down 27% to $2.43 in premarket trading.
The phase 2 study is testing Cardiff’s PLK1 inhibitor onvansertib in combination with standard of care in patients with first-line RAS-mutated metastatic colorectal cancer (mCRC). In December, the biotech reported a 64% objective response rate (ORR) on the high dose, compared to a 33% ORR in the control cohort. The gap between the treatment and control arms narrowed in the latest, larger cut of the data.
Including unconfirmed responses, the ORR was 59% on the high dose, versus a 43% response rate in the control arm. Removing the unconfirmed responses resulted in ORRs of 49% and 30%, respectively, for the high-dose and control arms. The difference fell short of the 20% targeted by Cardiff, William Blair analysts said in a note to investors. The analysts said the slight miss does not alter onvansertib’s profile.
Talking on a conference call with analysts, Cardiff CEO Mark Erlander said the data support "the next step in our path towards a seamless registrational trial for both accelerated and full approval.” Erlander’s position is built on the belief that the high dose is “clearly outperforming” the control group and that the data compare "favorably against previous practice-changing trials.”
Asked by an analyst whether Cardiff would wait for the data to mature before talking to the FDA, Erlander said, “I think we have to make that call in the next month or two.” The company is “right in the middle of a lot of the PK exposure response data,” the CEO said, but, as it stands, management believes it has the evidence to move forward and to speak with the FDA later in the year.
The progression-free survival (PFS) data that could provide a clearer picture of the impact of onvansertib are immature. Median PFS in the first-line setting is nine to 12 months, Erlander said. Cardiff has a median of six months of follow-up. The data that are available show a separation of the PFS curves, with the high dose performing best and the control performing worst, and Erlander believes the signs are encouraging.
“Early tumor shrinkage, early responses and depth of response are strongly correlated with improvements in progression-free survival,” the CEO told analysts. “We’re expecting those separations to continue and hopefully become even more clear with more patient follow-up.”
Cardiff is aiming to provide an update on the first-line mCRC program in the first quarter of next year.