AstraZeneca is capping out-of-pocket costs for inhalers and related medication at no more than $35 per month, the drugmaker announced Monday.

The Britain based pharma giant said the expanded savings are intended to help vulnerable patients with asthma or chronic obstructive pulmonary disease, especially those without health insurance. The price cap takes effect June 1.

“AstraZeneca’s expanded savings programs build on our long-standing commitment to addressing barriers to access and affordability for patients living with respiratory diseases to ultimately help patients lead healthier lives,” AstraZeneca chief executive Pascal Soriot said in a statement.

The move matches a cost-reduction program from Boehringer Ingelheim, a German pharmaceutical company that rivals AstraZeneca in the inhaler market. It follows the launch of an investigation by the Senate Committee on Health, Education, Labor and Pensions, in which Democratic senators and Sen. Bernie Sanders (Vt.), an independent who caucuses with the Democrats, wrote to four major inhaler companies asking them to lower prices.

Sanders released a statement Monday congratulating AstraZeneca and urging other companies to follow suit. The other two leading manufacturers — GlaxoSmithKline and Teva — have not agreed to a price cap.

The lawmakers have pointed to sizable differences in inhaler co-pays between the United States and Europe. For example, GlaxoSmithKline charges $319 for Advair HFA, a prescription inhaler, in the United States compared with $26 in Britain, according to the lawmakers.

“If AstraZeneca and Boehringer Ingelheim can cap the cost of inhalers at $35 in the United States, these other companies can do the same,” Sanders said in Monday’s release.

A GlaxoSmithKline spokesperson said in an email that the company “has a strong track record of responsibly pricing medicines while creating solutions that provide patients with access to scientific breakthroughs.” The company provides medicines and vaccines at no cost to patients who are eligible for its charitable programs, the spokesperson added.

Teva did not immediately respond to a request for comment.

The Asthma and Allergy Foundation of America, a patient advocacy group, said it welcomes efforts to make asthma drugs more affordable and called on health-care industry stakeholders to do their part to reduce costs.

“Drug manufacturers, pharmacy benefit managers, insurers, employers, and the government operate in a perverse system that drives prices higher — and all stakeholders must work together to improve affordability and access,” AAFA President Kenneth Mendez said in a statement.