Zentalis Pharmaceuticals Inc. (NASDAQ:ZNTL) received a bullish initiation from William Blair on Tuesday, which sees a potential blockbuster opportunity for the biotech company's lead cancer drug, azenosertib.

William Blair analyst Matt Phipps initiated coverage of Zentalis with an Outperform rating.

The firm's thesis centers on azenosertib, an oral WEE1 inhibitor being developed for Cyclin E1-positive platinum-resistant ovarian cancer, or PROC.

DENALI Data Could Unlock Accelerated Approval

William Blair identified the registration-enabling Phase 2 DENALI trial as Zentalis' most important near-term catalyst.

Top-line results from DENALI Part 2 are expected in the first half of 2027. William Blair said positive results could support an accelerated approval filing and give azenosertib a first-mover advantage in Cyclin E1-positive PROC. That biomarker-defined group represents roughly half of PROC patients.

The firm expects azenosertib could deliver a response rate above 30% and response durability of more than six months in DENALI Part 2. Earlier DENALI Part 1b data showed an approximately 35% overall response rate and a median duration of response of 6.3 months.

The Phase 3 ASPENOVA trial is designed to confirm the drug's benefit and potentially support full approval.

William Blair Sees $1.3 Billion Peak Sales

William Blair estimates a potential 2028 launch for azenosertib. The firm projects peak worldwide sales of about $1.3 billion and calculates a risk-adjusted net present value of $8.23 per Zentalis share, including net cash.

Its model assumes peak U.S. penetration of 50% in 2033, monthly pricing of $38,000 and a median treatment duration of six months. Those assumptions translate to roughly $800 million in peak U.S. sales and $1.3 billion worldwide.

William Blair also pointed to the rapid adoption of AbbVie Inc.'s (NYSE:ABBV) Elahere as evidence of demand for biomarker-directed treatments in PROC. The firm expects Elahere to exceed $850 million in sales in 2026.

Improved Tolerability Could Differentiate Azenosertib

A key part of William Blair's bullish thesis is azenosertib's selectivity for WEE1 compared with AstraZeneca PLC's (NYSE:AZN) discontinued WEE1 inhibitor adavosertib.

The firm said azenosertib's greater kinase selectivity, intermittent dosing and improved supportive care have reduced the severity of gastrointestinal and myelosuppression-related side effects. William Blair believes that could help patients remain on treatment longer and improve the durability of benefit.

Zentalis selected a 400-milligram daily, five-days-on and two-days-off regimen for DENALI Part 2. William Blair noted that this dose produced a higher response rate than the 300-milligram regimen with a comparable safety profile. Discontinuations due to adverse events were also roughly half the rate seen in DENALI Part 1b.

Clinical, Competition And Funding Risks Remain

The opportunity carries significant risks. DENALI Part 2 and ASPENOVA have yet to confirm earlier efficacy and safety findings. William Blair said weaker-than-expected DENALI response rates could jeopardize the accelerated approval pathway and potentially push an approval decision toward the ASPENOVA timeline.

Competition is also increasing. Incyte Corporation (NASDAQ:INCY) is developing the CDK2 inhibitor INCB123667 in Cyclin E1-positive PROC, while several antibody-drug conjugates are targeting the broader ovarian cancer market.

Zentalis had $174.6 million in cash and marketable securities as of June 30. Including proceeds from an August public offering, management expects its cash runway to extend into the first half of 2028.

William Blair cautioned that the company will likely need additional capital to fund development and potential commercialization.

ZNTL Price Action: Zentalis Pharmaceuticals shares were down 2.08% at $3.06 at the time of publication on Wednesday, according to market data.