IO Biotech Phase 3 Topline: PFS 19.4 vs 11.0 Months, HR 0.77 (IOBT)

IO Biotech disclosed topline results from its Phase 3 IOB-013 study evaluating Cylembio plus pembrolizumab versus pembrolizumab alone as first-line treatment for unresectable or metastatic melanoma.

Rhea-AI Filing Summary

IO Biotech disclosed topline results from its Phase 3 IOB-013 study evaluating Cylembio plus pembrolizumab versus pembrolizumab alone as first-line treatment for unresectable or metastatic melanoma. The randomized trial enrolled 407 patients (203 combination, 204 monotherapy). The primary endpoint, progression-free survival assessed by blinded independent review per RECIST v1.1, showed early and sustained separation with a hazard ratio (HR) of 0.77 (95% CI: 0.58–1.00; p=0.056), and median PFS of 19.4 months versus 11.0 months. The primary result falls short of the prespecified significance threshold.

Notable subgroup findings include a pronounced benefit in PD-L1 negative tumors (HR 0.54; mPFS 16.6 vs 3.0 months; nominal p=0.006) and in patients without prior anti–PD-1 therapy (post hoc HR 0.74; mPFS 24.8 vs 11.0 months; nominal p=0.037). Overall survival trends were favorable but immature (HR 0.79; 95% CI: 0.57–1.10). The combination was generally well tolerated; injection site reactions were most common (reported in 56% of combination arm patients) and resolved on treatment. The company plans regulatory discussions about a potential BLA and will present more detailed data. It disclosed an estimated cash balance of approximately $28.1 million plus a €12.5 million tranche drawn under a term loan, which it expects to fund operations into the first quarter of 2026, subject to final close procedures.

Positive

• Median PFS improved to 19.4 months with the combination versus 11.0 months with pembrolizumab alone
• Strong subgroup benefit in PD-L1 negative patients (HR 0.54; mPFS 16.6 vs 3.0 months; nominal p=0.006)
• Post hoc anti–PD-1 naive subgroup showed improved PFS (HR 0.74; mPFS 24.8 vs 11.0 months; nominal p=0.037)
• No new safety signals; combination generally well tolerated with mostly transient injection site reactions
• Regulatory engagement planned to discuss potential BLA submission based on the totality of data

Negative

• Primary endpoint narrowly missed statistical significance (HR 0.77; p=0.056; prespecified threshold p≤0.045)
• Overall survival immature with only a trend observed (HR 0.79; 95% CI: 0.57–1.10)
• Several key analyses are post hoc or nominally significant, which limits their regulatory weight
• Limited cash runway: estimated ~$28.1 million plus a €12.5 million tranche expected to fund into Q1 2026, indicating near-term financing need
• Preliminary cash estimate may change because financial closing procedures for the period are incomplete

Insights

Oncology Clinical Development Specialist

TL;DR: Positive PFS signals across key subgroups, but the primary endpoint narrowly missed statistical significance.

The trial enrolled 407 patients and showed an overall PFS HR of 0.77 (p=0.056), demonstrating an early and sustained separation of curves and a clinically meaningful median PFS increase to 19.4 months versus 11.0 months. The most compelling evidence is in PD-L1 negative patients (HR 0.54; mPFS 16.6 vs 3.0 months) and in anti–PD-1 naive patients (post hoc HR 0.74; mPFS 24.8 vs 11.0 months). However, the nominal subgroup p-values and a post hoc analysis do not replace a statistically significant primary outcome, so regulatory discussions will hinge on the totality of evidence, consistency of effect, and durability of OS as it matures.

Biotech Financial Analyst

TL;DR: Encouraging clinical signals tempered by missed primary significance and limited near-term cash runway.

The topline PFS improvement suggests clinical value that could support regulatory engagement, especially given strong PD-L1 negative and anti–PD-1 naive subgroup results. Nonetheless, missing the prespecified p-value raises regulatory and commercial risk; confirmatory evidence and mature OS will be pivotal. Financially, the company reports approximately $28.1 million in cash plus a €12.5 million loan tranche expected to fund operations into Q1 2026, indicating a need to secure additional capital within the next several quarters unless revenues or additional financing materialize. Investors should view this as a mixed outcome with both upside potential and near-term funding pressure.

8-K Event Classification

Item 8.01 — Other Events

1 item

Item 8.01 Other Events Other

Voluntary disclosure of events the company deems important to shareholders but not covered by other items.

FAQ

What were the primary topline results from IO Biotech (IOBT) Phase 3 IOB-013 trial?

The trial showed median PFS of 19.4 months for Cylembio plus pembrolizumab versus 11.0 months for pembrolizumab alone, with an overall HR of 0.77 (95% CI: 0.58–1.00; p=0.056).

Did IOB-013 meet its primary endpoint?

No. The primary PFS endpoint narrowly missed the prespecified significance threshold (p=0.056; threshold p≤0.045).

Were any subgroups showing stronger benefit in the IOB-013 study?

Yes. PD-L1 negative patients showed HR 0.54 with mPFS 16.6 vs 3.0 months (nominal p=0.006); a post hoc anti–PD-1 naive subgroup showed HR 0.74 with mPFS 24.8 vs 11.0 months (nominal p=0.037).

What did the company report about overall survival (OS)?

OS showed a favorable trend (HR 0.79; 95% CI: 0.57–1.10) but is not yet mature and is expected to mature over the next six to nine months.

What safety findings were reported for the combination treatment?

The combination was generally well tolerated; no new safety signals were observed and injection site reactions were the most common event (reported in 56% of combination arm patients) and resolved on treatment.

How long is IO Biotech's reported cash runway expected to last?

Estimated cash and cash equivalents of ~$28.1 million plus a €12.5 million tranche drawn under a term loan are expected to fund working capital into the first quarter of 2026, subject to final closing procedures.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 08/11/2025 - 08:00 AM Learn about SEC filing dates

false 0001865494 0001865494 2025-08-11 2025-08-11

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(D)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): August 11, 2025

IO BIOTECH, INC.

(Exact name of Registrant as Specified in its Charter)

Delaware		001-41008		87-0909276
(State or other jurisdiction of incorporation)		(Commission File Number)		(IRS Employer Identification No.)

Ole Maaløes Vej 3

DK-2200 Copenhagen N

Denmark

(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code: +45 7070 2980

N/A

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock, par value $0.001 per share		IOBT		The Nasdaq Stock Market LLC

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 2.02. Results of Operations and Financial Condition.

As discussed below, IO Biotech, Inc., a Delaware corporation (the “Company”), is hosting a conference call and webcast, during which the Company will make a slide presentation. In the slide presentation, the Company is disclosing an estimated cash and cash equivalents balance of approximately $28.1 million as of June 30, 2025, and further disclosing that the Company estimates that these cash and cash equivalents, plus the €12.5 million drawn on July 4, 2025 from the second tranche of the term loan facility with the European Investment Bank, will be sufficient to meet its working capital requirements into the first quarter of 2026.

Because the Company’s financial closing procedures as of and for the six months ended June 30, 2025, are not yet complete, its final results upon completion of those procedures may differ materially from its preliminary estimate. Accordingly, you should not place undue reliance on this preliminary estimate.

Item 7.01. Regulation FD Disclosure.

On August 11, 2025, the Company issued a press release announcing topline results from IOB-013, the Company’s Phase 3 trial of Cylembio® in combination with pembrolizumab as a first-line treatment for patients with unresectable or metastatic (advanced) melanoma. The Company is hosting a conference call and webcast at 8:30 am Eastern Time, on August 11, 2025, during which the Company will discuss the topline results and will make a slide presentation.

The press release is attached as Exhibit 99.1 and the form of slide presentation is attached as Exhibit 99.2, and each is incorporated into this Item 8.01 by reference.

The information contained in this Current Report on Form 8-K is being furnished and shall not be deemed to be “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section and shall not be incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such filing.

Item 8.01. Other Events

The randomized, open-label study enrolled 407 patients across more than 100 sites worldwide. Patients received either Cylembio in combination with pembrolizumab (n=203) or pembrolizumab alone (n=204). The primary endpoint was PFS as assessed by a blinded independent review committee per RECIST v1.1. The early and sustained separation of PFS curves demonstrated an improvement with a hazard ratio of 0.77 [95% CI: 0.58-1.00; p=0.056; threshold for significance p≤0.045]. Based on an intent-to-treat analysis, patients in the study treated with Cylembio in combination with pembrolizumab achieved 19.4 months of median progression free survival compared to 11.0 months in patients treated with pembrolizumab alone. Although not yet mature, a trend toward an improvement in overall survival was also observed [HR 0.79 (95% CI: 0.57-1.10)]; the company expects OS to mature over the next six to nine months. Improvement in PFS was achieved across virtually all subgroups, including those with poor prognostic factors, with a profound effect in patients with PD-L1 negative tumors treated with Cylembio plus pembrolizumab (n=67) compared to patients treated with pembrolizumab monotherapy (n=63), HR: 0.54 (CI 0.35-0.85) (nominal p=0.006), with mPFS of 16.6 months vs. 3.0 months, respectively. Additionally, in a post hoc analysis of patients enrolled in this study without prior anti-PD-1 treatment (n=371), patients treated with Cylembio plus pembrolizumab achieved improvement in PFS compared to patients treated with pembrolizumab monotherapy, HR: 0.74 (CI 0.56-0.98) (nominal p=0.037), with mPFS of 24.8 months vs. 11.0 months, respectively. The combination was well tolerated, with no new safety signals observed. Injection site reactions, which were transient and resolved on treatment, were the most commonly reported adverse events in the combination arm, with 56% of patients receiving Cylembio plus pembrolizumab reporting an event. Based on these results, the Company plans to meet with the regulatory authorities to discuss the totality of data and determine next steps for submission of a Biologics License Application (BLA) for the treatment of advanced melanoma to the U.S. Food and Drug Administration (FDA). Additionally, the Company plans to present more detailed results from the IOB-013 study at an upcoming medical meeting.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits

Exhibit Number		Exhibit Description
99.1		IO Biotech, Inc. Press Release, dated as of August 11, 2025
99.2		IO Biotech, Inc. Presentation
104		Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

				IO BIOTECH, INC.
Date: August 11, 2025				By:		/s/ Mai-Britt Zocca, Ph.D.
				Name:		Mai-Britt Zocca, Ph.D.
				Title:		Chief Executive Officer