Andris (Andy) Zoltners, who cofounded ZS Associates with Prabha Sinha in 1983, died on April 11 after a long struggle with Parkinson’s disease. He was 77.

Zoltners played a pivotal role in growing the consultancy from a two-person operation to a global giant with more than 12,000 employees in 35 offices across 15 countries. He was honored alongside Sinha with a lifetime achievement award by the Pharmaceutical Management Science Association in 2012, and was inducted into the University of Illinois at Chicago’s Chicago Area Entrepreneurship Hall of Fame in 2005.

Zoltners was a faculty member at the Kellogg School of Management at Northwestern University for more than 30 years.

In a memo sent to ZS employees, CEO Pratap Khedkar remembered Zoltners as an individual whose “vision and tenacity were matched only by his humility.” Here is the full text of the memo:

Remembering ZS Cofounder Andy Zoltners

It’s with great sadness that I share that Andy Zoltners, the “Z” in ZS, has passed away after a long and difficult battle with Parkinson’s disease. He will be deeply missed by the thousands of people whose lives he touched, especially his dear colleagues at ZS and our ZS alumni.

As a leader, Andy’s vision and tenacity were matched only by his humility. The foundation he laid, on which we’ve built ZS’s culture, values and commitment to excellence, is deep and indelible. What started as two people with a passion for problem-solving has now grown into a global firm of more than 12,000 proud ZSers, all of whom are indebted to Andy for his founding vision. Andy Zoltners and Prabha Sinha founded ZS on three core values: treat people right, do the right thing and get it right. With Andy’s passing, the ZS team has even more resolve to honor his memory by working every day to embody these principles and continue building our business on ethics, integrity and respect.

Andy’s passing happens to coincide with the 40th anniversary of the firm he took great pride in building from the ground up, starting all the way back in 1983. Andy built deep relationships across the biopharmaceutical landscape by helping clients solve their most complex business challenges. His desire to make an impact that truly mattered was an inspiration, and that mindset is what drives our passionate and dedicated people across 35 global offices today.

As we spend this year celebrating four decades of client impact, culture and an unwavering commitment to our core values, we now have one more thing to celebrate and pay tribute to: the legacy of Andy, an admirable man and extraordinary visionary.

I’m humbled to have the privilege — along with ZS people across the globe — to carry forward Andy’s guiding vision of transforming healthcare through our work with clients. You’ll be missed, Andy.

Pratap Khedkar, CEO