Breast Cancer Breakthrough: Gedatolisib Triplet Delays Progression to 21.5 Months in Key Patient Group

Patients with a common form of advanced breast cancer lived far longer without their disease worsening when treated with a three-drug combination built around gedatolisib, according to new trial results released on 24 October 2026 — but the benefit was clearest in one patient group, and the results do not yet amount to a new drug approval.

Illustration: A scientist at work in a medical research laboratory, symbolising the clinical trial behind the new results.

What Happened

Drugmaker Celcuity reported updated subgroup results from the Phase 3 VIKTORIA-1 trial of gedatolisib, a drug sold as REVTORPYK, in patients with PIK3CA-mutant, hormone-receptor-positive, HER2-negative advanced breast cancer whose disease had progressed after earlier hormone-based treatment. The headline finding concerns patients without liver metastases: those who received the gedatolisib triplet — gedatolisib plus fulvestrant and palbociclib — had a median progression-free survival of 21.5 months, compared with 9.1 months for patients who received alpelisib plus fulvestrant.

Progression-free survival measures how long patients live before their cancer grows or spreads further; it is not the same as overall survival, and the new results do not claim a survival advantage. The difference in the no-liver-metastases group carried a hazard ratio of 0.46, meaning the risk of progression or death at any given time was roughly halved, with a p-value of 0.0016. The triplet group in this analysis included 77 patients, and the control group 76.

The same update showed benefits in other subgroups too. In patients with liver metastases, the triplet's median progression-free survival was 9.1 months versus 4.6 months for the control regimen, with a hazard ratio of 0.47. Tumours shrank in 59% of patients on the triplet across the mutant cohort (counting confirmed and unconfirmed responses), compared with 43% on the two-drug gedatolisib doublet and 33% on alpelisib plus fulvestrant.

Background

VIKTORIA-1 is a Phase 3 trial in adults with HR-positive, HER2-negative locally advanced or metastatic breast cancer — the most common subtype of advanced breast cancer — whose disease progressed during or after treatment with a CDK4/6 inhibitor and an aromatase inhibitor, two standard hormone-based therapies. The trial, listed on ClinicalTrials.gov as NCT05501886, has an estimated enrolment of 701 patients and is described as active but no longer recruiting.

Gedatolisib is already an approved drug, but not for the patients in this update. On 14 July 2026, the US Food and Drug Administration (FDA) approved gedatolisib with fulvestrant, with or without palbociclib, for adults with the same type of breast cancer without a detected PIK3CA mutation, after at least one line of hormone therapy in the metastatic setting. That approval was based on Study 1 of VIKTORIA-1, in which 392 patients were randomised; the triplet's median progression-free survival was 9.3 months versus 2.0 months for fulvestrant alone.

Illustration: A doctor consulting with a patient in a hospital room, reflecting the treatment decisions these results may inform.

The 24 October update is different: it looks at Study 2, the PIK3CA-mutant cohort — patients whose tumours carry a mutation in the PIK3CA gene, which helps drive cancer growth. Celcuity said in August 2026 that it had submitted an application seeking use of gedatolisib in this mutant population, but the October update did not announce an FDA decision on that application. In other words, the new numbers are subgroup findings from a trial, not a new approved use.

Safety results were also reported. Treatment stopped because of side effects in 5% of triplet patients and 4% of doublet patients, compared with 19% of patients receiving alpelisib. Celcuity said severe mouth inflammation (grade 3 stomatitis) had fallen to less than 3% of patients by the second treatment cycle, and that treatment stops for stomatitis were 1% or less.

Why It Matters

For patients whose cancer has already progressed on standard hormone therapy, options narrow quickly, and the gap between 21.5 and 9.1 months of stable disease is clinically meaningful — more than a year of additional time before the cancer worsens, for the group without liver spread. Celcuity notes that patients without liver metastases make up roughly 60% to 70% of people treated in this setting, so the finding, if confirmed, could apply to a majority of this population.

The results also matter because they test a long-standing question in breast cancer treatment: whether blocking the PI3K pathway — the signalling route in which the PIK3CA gene plays a central role — can restore sensitivity to hormone therapy after resistance has developed. The response rates and the duration of response (a median of 19.4 months for the triplet, versus 7.5 months for the control) suggest the combination is doing more than marginally delaying progression, though response rates here count both confirmed and unconfirmed responses, which is a more generous measure than confirmed responses alone.

At the same time, the caveats are substantial and should not be skipped. Subgroup analyses slice a trial into smaller groups after the fact, and small groups can produce striking numbers by chance. The doublet comparison in the no-liver-metastases group, for example, did not reach statistical significance (median 11.5 months in just 28 patients, p=0.1627), and some cells in the analysis are very small — the doublet group with liver metastases had only 24 patients. Overall survival data were not mature in the earlier approval, and the October update does not change that picture.

What Happens Next

The key next step is regulatory: whether the FDA extends gedatolisib's approval to the PIK3CA-mutant population on the basis of the mutant cohort data. Celcuity's application for that population was submitted in August 2026, and no decision was announced in the October update. Doctors and patients will also be watching for fuller presentations of the data, including overall survival as it matures and results broken down by other patient characteristics.

Illustration: Medicine vials and molecular structures on a laboratory bench, symbolising targeted cancer drug research.

For now, the practical message is narrow but encouraging: in one well-defined group of patients with hard-to-treat advanced breast cancer, a three-drug regimen more than doubled the time before the disease progressed compared with the control treatment. Whether that becomes a new standard option depends on regulators weighing exactly these subgroup numbers — and their limits — in the months ahead.

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FAQ

What is gedatolisib?

Gedatolisib (brand name REVTORPYK) is a drug made by Celcuity that blocks the PI3K/mTOR signalling pathway, which helps some breast cancers grow. It is given by intravenous infusion alongside the hormone therapy fulvestrant, with or without palbociclib.

What did the new results actually show?

In PIK3CA-mutant patients without liver metastases, the gedatolisib triplet kept cancer stable for a median of 21.5 months, versus 9.1 months on alpelisib plus fulvestrant. In patients with liver metastases, the figures were 9.1 versus 4.6 months. These are progression-free survival results, not overall survival.

Is gedatolisib now approved for PIK3CA-mutant breast cancer?

No. The FDA's July 2026 approval covers patients without a detected PIK3CA mutation. The October 2026 update reports subgroup results for the mutant cohort; Celcuity's application for that population was submitted in August 2026, with no decision announced in the update.

How safe was the treatment?

According to Celcuity, treatment stopped because of side effects in 5% of triplet patients and 4% of doublet patients, versus 19% on alpelisib. Severe mouth inflammation had fallen below 3% by the second cycle.

What are the main caveats?

The results come from subgroup analyses with some small patient groups, so individual numbers should be read cautiously. The doublet comparison in the no-liver group was not statistically significant, response rates include unconfirmed responses, and overall survival data are not yet mature.

Sources

• Celcuity, VIKTORIA-1 Phase 3 subgroup results, reported 24 October 2026 (via NovaPharmaNews and TokenPost coverage, 24 October 2026): 21.5 vs 9.1 months, hazard ratio 0.46, response rates 59% vs 33%.
• US Food and Drug Administration, gedatolisib approval note, 14 July 2026: approval limited to patients without a detected PIK3CA mutation; Study 1 median progression-free survival 9.3 vs 2.0 months.
• ClinicalTrials.gov, VIKTORIA-1 (NCT05501886): trial status active, not recruiting; estimated enrolment 701.