Ibrance trial halt threatens Pfizer’s growth targets

One trial of Pfizer’s drug in early breast cancer has been stopped, and expectations dim for another.

Trial Results

Ibrance is a big deal for Pfizer – but might never be a much bigger one. A great deal was riding on the Pallas study of the breast cancer blockbuster in early disease, and the findings of an interim analysis suggesting that the trial is unlikely to succeed have knocked the group badly. 

Pallas, along with another study called Penelope-B, was assessing Ibrance’s utility as an adjuvant treatment, alongside endocrine therapy. In January the company said approval in this setting could double the number of patients eligible for treatment with the CDK 4 and 6 inhibitor. This now looks doubtful, and Pfizer’s stock is off 6% in early trading.

Ibrance is approved globally for metastatic HR-positive, Her2-negative breast cancer, and sold $5.0bn for Pfizer last year. The group was running Pallas and Penelope-B in the hope that they would allow the drug’s approval earlier in the treatment sequence; partly owing to expectations here, the sellside has pencilled in sales of $11bn in 2026, according to EvaluatePharma consensus. 

Pallas randomised nearly 6,000 subjects with HR-positive, Her2-negative early breast cancer to a daily Ibrance 125mg pill for three weeks followed by a week off treatment, with the cycle continued for two years, in addition to standard adjuvant endocrine therapy, or endocrine therapy alone. The aim was to show a significant improvement in invasive disease-free survival. 

Growth driver

This is not, it seems, going to happen, and the implications for the ongoing Penelope-B, in the same setting but a slightly different population, are not good. And even if Penelope-B does hit, it will be the lesser prize. The patient population corresponding to that trial is thought to be around 62,000 strong in G7 countries; had Pallas hit, the addressable G7 population would have been more like 150,000 patients.

Trials of Ibrance in early breast cancer
Trial Details Results
Pallas 5,796 men and women with HR+/Her2-ve early breast cancer Stopped for futility
Penelope-B 1,250 women with HR+/Her2-normal early breast cancer Expected early 2021
Source: EvaluatePharma, clinicaltrials.gov.

There is a crumb of comfort in the fact that expectations for similar trials of competing drugs, such as Lilly’s MonarchE study of Verzenio and Novartis’s Natalee trial of Kisquali, are not earth-shattering either.

The real issue is what the Pallas failure means for Pfizer’s growth expectations. Chief executive Albert Bourla insisted that he was “highly confident” that Pfizer could still deliver on its goal of at least 6% revenue growth each year to 2025. The need to hit this target piles even more pressure on the group’s other high-profile projects, such as Braftovi and Mektovi and the eczema asset abrocitinib. 

Abrocitinib acquitted itself well against Regeneron’s Dupixent in the phase III Jade Compare trial, though the Jak is not without safety concerns. According to EvaluatePharma sellside consensus, its 2026 forecasts stand at $765m, a long way behind the billions that had been expected for Ibrance had Pallas succeeded. 

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