IMpassion131
IMpassion131 was the sister trial to the first immunotherapy success in breast cancer. It failed, and the approval it was meant to confirm was withdrawn.
IMpassion130 (nab-paclitaxel partner) had shown a PFS benefit in PD-L1-positive metastatic TNBC and won accelerated approval in 2019. IMpassion131 used conventional paclitaxel (which requires steroid premedication) and showed no PFS or OS benefit; OS trended worse in the atezolizumab arm. Roche withdrew the US TNBC indication in 2021. Pembrolizumab with chemotherapy (KEYNOTE-355) became the standard instead.
Lesson: the chemotherapy partner (steroid premedication, immunogenic cell death profile) and the PD-L1 assay (SP142 vs 22C3) can decide an immunotherapy trial; confirmatory trials must replicate the winning design.
- Median 6 vs 5.7 months with Atezolizumab + paclitaxel compared with Placebo + paclitaxel; about 0.3 months longer for half the group.
- A median is a midpoint: half the people did better than this and half did worse, so it is not a prediction for any one person.
- Put another way, the treated group had about 18 percent lower chance of the event at any given time (hazard ratio 0.82, likely range 0.6 to 1.12).
- This is a surrogate endpoint: it measures the cancer being controlled or absent on scans and tests, which often, but not always, translates into living longer.
- Not significant.
- Median 22.1 vs 28.3 months with Atezolizumab + paclitaxel compared with Placebo + paclitaxel; about 6.2 months shorter for half the group.
- A median is a midpoint: half the people did better than this and half did worse, so it is not a prediction for any one person.
- Put another way, the treated group had about 11 percent higher chance of the event at any given time (hazard ratio 1.11, likely range 0.76 to 1.64).
- Overall survival counts deaths from any cause, so it is the most direct measure of whether a treatment helps people live longer.
- The likely range for the hazard ratio crosses 1, so the difference could be due to chance.
- These results apply to the people the trial enrolled: First-line metastatic TNBC: atezolizumab + paclitaxel vs paclitaxel. People in a different situation may not see the same effect.
Numbers are from the trial as recorded here; see the source links in the table below. This is orientation, not medical advice: ask your team how closely the trial population matches you.
651 participants enrolled.
Not significant
SourceNumerically unfavourable
Source| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Progression-free survival, PD-L1+ (investigator)primary | Atezolizumab + paclitaxel | 191 | 6 months | 0.82 (0.6–1.12) | 0.20 | link |
| Placebo + paclitaxel | 101 | 5.7 months | ||||
| Overall survival, PD-L1+ | Atezolizumab + paclitaxel | — | 22.1 months | 1.11 (0.76–1.64) | — | link |
| Placebo + paclitaxel | — | 28.3 months |
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Shares Triple-negative breast cancer (TNBC) and the tag failure.
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Shares Paclitaxel / nab-paclitaxel and the tag failure.
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Shares Triple-negative breast cancer (TNBC) and the tag failure.