More than 160 biotech and VC execs have signed a strongly worded letter in Nature Biotech today denouncing President Donald Trump’s recent three-month immigration executive order that has delayed or banned some travelers from across seven predominantly Muslim countries trying to enter the U.S.

The biotech and venture capital leaders (which include industry vets Jeremy Levin, the former Teva CEO and now Ovid chief, as well as Incyte’s head Herve Hoppenot and VC Flagship’s Michael Rosenblatt) shared their concerns that the order will strip the U.S. of its life science leadership, halt the fight against disease, and instill fear into the early-stage biotech industry. This also comes as judges are attempting to block the order.

In the letter, the CEOs said, “We the undersigned, founders and leaders of biotech companies, write to express our deep concern and opposition to the executive order signed by President Donald Trump on January 27, 2017, barring the entry of citizens from seven countries into the United States."

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“Our success has been founded on the creativity and dedication of our most precious resource—our people. Our people include researchers, clinicians, entrepreneurs and business executives from all over the world. They are colleagues in our laboratories, management teams and boardrooms.

“And they start companies that drive the economic growth and employment provided by biotech. Many of our colleagues from abroad ultimately become Americans, all to the great benefit of the United States. Indeed, a study found that in 2014, 52% of the 69,000 biomedical researchers in the United States were foreign-born.”

But it warned that, “at a stroke, the new administration has compromised years of investment in this national treasure.”

The letter continued: “Our colleagues who are here on visas or are in global outposts are now fearful and uncertain of their status. Scientists based in other countries and employed by our companies are afraid to come to the United States or are canceling trips. The parents and families of immigrants who live and work in the United States are reluctant to attempt to travel to and from the U.S.”

The CEOs said that although the ruling was aimed at seven countries, its global impact is being seen as: “America is no longer welcoming of any immigrants, whatsoever.” And immigrants or travelers fear similar orders could be issued for other countries at a moment’s notice.

“They fear being stigmatized and discriminated against, simply because of their religion, irrespective of the nation they come from. Several among us have heard from employees about their deportation fears, how they do not feel comfortable leaving the country on business or how they now feel cut off from their family abroad.”

They believe Trump’s actions were “poorly conceived and implemented; they have raised deep fears and concerns across the biotech industry, in which diversity and the free flow of ideas and people have created an American powerhouse of medicine.”

The signatories concluded: “If this misguided policy is not reversed, America is at risk of losing its leadership position in one of its most important sectors, one that will shape the world in the twenty-first century. Indeed, it will harm an industry dominated by smaller companies and startups, the very kind of industry the administration has said it wants to support. It will slow the fight against the many diseases that afflict us, as well as carry negative economic consequences for the United States.”

Trump has remained adamant that the order is intended to protect Americans from possible terrorist threats, but it has earned the ire of companies who rely on the free flow of people in and out of the country.

Just this week, Apple, Microsoft, Google and around 100 other tech firms all filed a legal brief against the administration and its order. But pharma has been a lot quieter and, despite U.S. Big Pharma chiefs meeting with Trump just last week, the topic of immigration and his order was not on the agenda, with Allergan’s CEO Brent Saunders one of only a few voices coming out against Trump.

There has been a lot of bullish optimism that Trump could help boost biopharma M&A this year with a promise to lower regulation, and speed up approvals at the FDA, as well as unlocking overseas cash and a general focus on promoting business, but his immigration policies may just be taking the edge of the so-called Trump bump in stocks.