Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer. It accounts for roughly **15% of all breast cancers**, but is disproportionately represented among the most serious cases — it tends to occur in younger women, grows faster than hormone-driven breast cancers, and lacks the molecular targets (estrogen receptors, progesterone receptors, HER2) that have made other breast cancer subtypes highly treatable with targeted therapy.
For TNBC, the front line remains a gruelling, months-long combination of chemotherapy and immunotherapy (typically pembrolizumab) before surgery. The goal is **pathological complete response (pCR)** — no cancer detectable in the surgically removed tissue — a measure that strongly predicts long-term survival. Standard treatment achieves pCR in roughly **30–40%** of patients with tumours similar in size to those in the INVINCIBLE-4 study.
Early data from a small but striking Phase 2 trial suggests that adding a single drug — delivered directly into the tumour — may more than double that rate.
**What INT230-6 Is**
**INT230-6** is an investigational cancer treatment developed by **Intensity Therapeutics** (Nasdaq: INTS). It uses the company's proprietary **non-covalent drug conjugation (SHAO) technology** to combine two established chemotherapy agents — **cisplatin** and **vinblastine** — into a formulation designed to be injected directly into a solid tumour.
The approach is called **intratumoral injection**, and the logic behind it is compelling: rather than flooding the entire body with toxic chemotherapy agents and accepting all the systemic side effects that implies, you deliver the drugs precisely where they're needed — inside the tumour itself.
But INT230-6 is designed to do more than kill tumour cells locally. The formulation is engineered to diffuse through tumour tissue while remaining largely contained within the tumour, and to trigger **immunogenic cell death** — the kind of tumour cell destruction that activates the immune system, recruiting T-cells and other immune cells to recognise and attack the cancer more broadly.
In other words: it kills cells at the injection site *and* it makes the tumour visible to the immune system — potentially amplifying the effect of the immunotherapy (pembrolizumab) already being given.
**The INVINCIBLE-4 Study: Early Data**
The INVINCIBLE-4 Study is a Phase 2 presurgical study being conducted in Switzerland, evaluated by Swiss regulatory authority **Swissmedic** and the Swiss Ethics Committee. It enrolled patients with triple-negative breast cancer with tumours of 1.5 cm or larger.
Patients are divided into two groups:
- **Cohort A:** INT230-6 injections into the tumour *plus* standard of care (the Keynote-522 regimen: pembrolizumab, paclitaxel, carboplatin, and doxorubicin or epirubicin with cyclophosphamide over 6 months) - **Cohort B:** Standard of care alone
In **March 2026**, the company released preliminary data from the first 14 patients treated (7 per arm).
The early results:
✅ **Cohort A (INT230-6 + SOC): 5 out of 7 patients achieved pCR — 71.4%** ⬜ **Cohort B (SOC alone): 2 out of 6 patients achieved pCR — 33%** (one patient still awaiting evaluation)
And on tolerability:
🟢 **Cohort A: 14 total grade 3+ adverse events** 🔴 **Cohort B: 25 total grade 3+ adverse events** — **44% more**
Not only did more patients in the INT230-6 arm achieve the treatment goal. They experienced fewer serious side effects doing it.
**The Essential Caveats**
These results are **preliminary and early**, and honesty requires saying so clearly.
The trial has treated only 14 patients in total — 7 per arm. In clinical science, this is a very small number. The pCR comparison (5/7 vs 2/6) could shift meaningfully with additional patients. The trial is also ongoing, with a planned total enrolment of up to 61 patients, meaning the final results may look different.
Enrolment was also paused in September 2025 after skin irritations were observed in Cohort A — an important safety signal. A protocol amendment was submitted in early March 2026 to resume enrolment with a **lower drug volume per tumour volume ratio** and a **single injection** rather than multiple, intended to minimise the skin reaction while preserving efficacy.
Lewis H. Bender, Intensity's Founder and CEO, acknowledged the preliminary nature of the results: "The pCR data observations to date in the INVINCIBLE-4 study are promising, though preliminary and early."
**Why It Matters Anyway**
Small and early though the sample is, a 71% pCR rate in triple-negative breast cancer — achieved with *fewer* severe side effects than standard care — is a signal that demands attention.
pCR in TNBC is not just a technical benchmark. It predicts outcomes: patients who achieve pCR after neoadjuvant therapy have significantly lower rates of cancer recurrence and better long-term survival. Doubling the pCR rate, if confirmed in larger studies, would translate to real-world survival improvements for the most aggressive breast cancer subtype.
The fact that this is achieved by injecting a drug *into the tumour* — rather than the current approach of systemic chemotherapy that affects the entire body — also points toward a future where treatment can be both more effective and more tolerable.
The INVINCIBLE-4 study will need to complete enrolment and report its full results before this becomes practice-changing medicine. But the direction of travel is striking.
For triple-negative breast cancer patients and their families, watching these trials unfold — one small study at a time — this early signal is worth knowing about. 🩷🔬
*Sources: Intensity Therapeutics press release (March 2026) · PR Newswire · Swissmedic / Swiss Ethics Committee · Keynote-522 study regimen (Merck/Pembrolizumab) · Nasdaq: INTS · INVINCIBLE-4 Study design documentation*
