Pyxis Oncology Inc. (NASDAQ:PYXS) dropped some fresh data on Wednesday from its ongoing Phase 1 trial of micvotabart pelidotin (MICVO), and it's a bit of a mixed bag. The drug, tested as a monotherapy in patients with recurrent or metastatic head and neck squamous cell carcinoma who've already tried other treatments, showed some real promise. But there are also some safety red flags that have analysts and investors a little uneasy.

Let's start with the good stuff. In 33 evaluable patients who got 5.4 mg/kg of MICVO intravenously every three weeks, the treatment hit a 36% confirmed objective response rate and a 94% disease control rate. That's pretty solid for a tough-to-treat cancer. The median progression-free survival clocked in at 6.2 months, and while they haven't hit the median overall survival yet, the 12-month probability is sitting at 79%. Not too shabby.

The responses were seen across different subgroups, no matter what prior treatments patients had or their HPV status. And among the 35 people evaluated for safety, there were no new safety signals. The company also said that implementing a dose cap helped reduce the severity of adverse events in heavier patients. MICVO is an antibody-drug conjugate that targets the tumor extracellular matrix, which is a bit different from the usual approach.

Now, the not-so-good stuff. William Blair analyst Andy Hsieh, while encouraged by the response breadth and survival signals, pointed out that the safety profile is still a key liability. Here's the number that might make you wince: 54% of patients experienced grade 3 or higher treatment-related adverse events, and 14% of patients discontinued treatment because of them. That's a significant chunk, even with the dose capping in place.

Hsieh also noted the limitations of interpreting event-driven or landmark-based metrics like progression-free survival or one-year survival probability. In other words, these numbers can look good early on but might not hold up over time.

So what's next for Pyxis? The company plans to meet with the FDA in the first quarter of 2027 to finalize dose selection through Project Optimus. After that, they want to launch a 500-patient, open-label Phase 3 study in mid-2027, comparing MICVO against cetuximab, docetaxel, or methotrexate. That's a big trial, and it'll be the real test.

There's also a combination study in the works. Updated Phase 1/2 data on MICVO with Merck's KEYTRUDA is expected in the fourth quarter of 2026, with durability metrics and the recommended Phase 3 dosing for that combo coming by late 2027.

Investors didn't seem too thrilled with the news, sending shares down 9.25% to $3.53 at the time of publication on Wednesday. It's a reminder that in the biotech world, efficacy alone doesn't always win the day. Safety matters, and when you see a high rate of severe adverse events, the market gets nervous.

Still, this is early data, and the company has a clear path forward. The FDA meeting and the Phase 3 trial will be crucial. If MICVO can maintain its efficacy while managing the safety profile, it could be a significant player in head and neck cancer. But for now, the jury's still out.