This month, Mark Walker is celebrating his company's one year anniversary of going public — only the ninth Black-founded business to accomplish this feat on a U.S. stock exchange. Photo courtesy

After working in both sides of the advertising world, Mark Walker thought he could reimagine a platform that would be more efficient and equitable.

Walker co-founded his company, Direct Digital Holdings, an adtech platform, after serving in several roles — from an early hire at Houston digital media startup Questia to business development director at NRG Energy and COO of EBONY Media. He shares on the Houston Innovators Platform how he took this experience in tech, advertising, and media to create his company's platform.

"NRG Energy gave me a top-down view of the value chain, and Ebony gave me a bottoms-up view of the value chain of how media is purchased," Walker says on the show. "At Direct Digital Holdings, we help companies buy and sell media — and we leverage technology to do it. It's really the culmination of both of those experiences."

With over 30,000 publishers on its platform, Direct Digital makes it easier for its core customers — middle market companies looking to buy into the digital media ecosystem — to tap into these opportunities without the tech know-how they might otherwise need. Walker explains that at EBONY, he saw how small to midsize publications — especially the multicultural ones — were being left out on the ad selling side of the equation. The Direct Digital platform bridges the gap on each end.

Founded in 2018 in partnership with Keith Smith, who went through similar professional experiences, Direct Digital went public exactly one year ago after growing the company through strategic M&A activity. Walker says the decision to IPO made the most sense for his company — though it wasn't an easy process. Direct Digital is only the ninth company founded by a Black entrepreneur to go public on a US stock exchange.

"If you think the process is hard — it actually is," Walker says on the journey to IPO. "We were a privately held company, and we knew we had a good growth trajectory and we looked a couple different options. We decided to go public in a very traditional way."

Walker explains there were some risks involved, but the co-founders ultimately decided to shy away from adding in investors who might not have the same ideas for the company's future.

Direct Digital has been a Houston company from the star — despite the city not being home to a booming adtech ecosystem. Instead, Houston — with its collection of Fortune 500 companies and rich diversity — has allowed the business to stand out.

"If you look at and reflect on how our company has been built — from our board of directors to our leadership and management team — we're a majority minority organization all the way across the board," Walker says. "Diversity is very important to us. It's the lifeblood of our business — especially because we're serving publishers in those communities in big way. And moreso, we think you get the best product, thoughts, and ideas from a diverse workforce, and Houston fits right into that mold for us."

Walker shares more about his company's future, advice on IPO, and what all he's watching in adtech — from AI to streaming — on the podcast. Listen to the interview below — or wherever you stream your podcasts — and subscribe for weekly episodes.


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3 Houston innovators to know this week

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Editor's note: Welcome to another Monday edition of Innovators to Know. Today I'm introducing you to three Houstonians to read up about — three individuals behind recent innovation and startup news stories in Houston as reported by InnovationMap. Learn more about them and their recent news below by clicking on each article.

Sean Kelly, CEO and co-founder of Amperon

Amperon CEO Sean Kelly joins the Houston Innovators Podcast to share his company's growth and expansion plans. Photo via LinkedIn

The technology that Amperon provides its customers — a comprehensive, AI-backed data analytics platform — is majorly key to the energy industry and the transition of the sector. But CEO Sean Kelly says he doesn't run his business like an energy company.

Kelly explains on the Houston Innovators Podcast that he chooses to run Amperon as a tech company when it comes to hiring and scaling.

"There are a lot of energy companies that do tech — they'll hire a large IT department, they'll outsource a bunch of things, and they'll try to undergo a product themselves because they think it should be IP," he says on the show. "A tech company means that at your core, you're trying to build the best and brightest technology." Continue reading.

Amanda Burkhardt, CEO of Phiogen

Spun out of Baylor College of Medicine, Phiogen was selected out of 670 companies to pitch at SXSW earlier this month. Photo via LinkedIn

A new Houston biotech company won a special award at the 16th Annual SXSW Pitch Award Ceremony earlier this month.

Phiogen, one of 45 companies that competed in nine categories, was the winner for best inclusivity, much to the surprise of the company’s CEO, Amanda Burkhardt.

Burkhardt tells InnovationMap that while she wanted to represent the heavily female patient population that Phiogen seeks to treat, really she just hires the most skilled scientists.

“The best talent was the folks that we have and it ends up being we have three green card holders on our team. As far as ethnicities, we have on our team we have Indian, African-American, Korean, Chinese Pakistani, Moroccan and Hispanic people and that just kind of just makes up the people who helped us on a day-to-day basis,” she explains. Continue reading.

Mielad Ziaee, 2023-2024 All of Us Research Scholar

Mielad Ziaee, a 20-year-old student at the University of Houston, was tapped for a unique National Institutes of Health program. Photo via UH.edu

A Houston-area undergraduate student has been tapped for a prestigious national program that pairs early-career investigators with health research professionals.

Mielad Ziaee was selected for the National Institutes of Health’s 2023-2024 All of Us Research Scholar Program, which connects young innovators with experts "working to advance the field of precision medicine," according to a statement from UH. Ziaee – a 20-year-old majoring in psychology and minoring in biology, medicine and society who plans to graduate in 2025 — plans to research how genomics, or the studying of a person's DNA, can be used to impact health.

“I’ll be one of the ones that define what this field of personalized, precision medicine will look like in the future,” Ziaee said in a statement. “It’s exciting and it’s a big responsibility that will involve engaging diverse populations and stakeholders from different systems – from researchers to health care providers to policymakers.” Continue reading.

Health tech startup launches Houston study improve stroke patients recovery

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A Houston-born company is enrolling patients in a study to test the efficacy of nerve stimulation to improve outcomes for stroke survivors.

Dr. Kirt Gill and Joe Upchurch founded NeuraStasis in 2021 as part of the TMC Biodesign fellowship program.

“The idea for the company manifested during that year because both Joe and I had experiences with stroke survivors in our own lives,” Gill tells InnovationMap. It began for Gill when his former college roommate had a stroke in his twenties.

“It’s a very unpredictable, sudden disease with ramifications not just for my best friend but for everyone in his life. I saw what it did to his family and caregivers and it's one of those things that doesn't have as many solutions for people to continue recovery and to prevent damage and that's an area that I wanted to focus myself on in my career,” Gill explains.

Gill and Upchurch arrived at the trigeminal and vagus nerves as a potential key to helping stroke patients. Gill says that there is a growing amount of academic literature that talks about the efficacy of stimulating those nerves. The co-founders met Dr. Sean Savitz, the director of the UTHealth Institute for Stroke and Cerebrovascular Diseases, during their fellowship. He is now their principal investigator for their clinical feasibility study, located at his facility.

The treatment is targeted for patients who have suffered an ischemic stroke, meaning that it’s caused by a blockage of blood flow to the brain.

“Rehabilitation after a stroke is intended to help the brain develop new networks to compensate for permanently damaged areas,” Gill says. “But the recovery process typically slows to essentially a standstill or plateau by three to six months after that stroke. The result is that the majority of stroke survivors, around 7.6 million in the US alone, live with a form of disability that prevents complete independence afterwards.”

NeuraStasis’ technology is intended to help patients who are past that window. They accomplish that with a non-invasive brain-stimulation device that targets the trigeminal and vagus nerves.

“Think of it kind of like a wearable headset that enables stimulation to be delivered, paired to survivors going through rehabilitation action. So the goal here is to help reinforce and rewire networks as they're performing specific tasks that they're looking to improve upon,” Gill explains.

The study, which hopes to enroll around 25 subjects, is intended to help people with residual arm and hand deficits six months or more after their ischemic stroke. The patients enrolled will receive nerve stimulation three times a week for six weeks. It’s in this window that Gill says he hopes to see meaningful improvement in patients’ upper extremity deficits.

Though NeuraStasis currently boasts just its two co-founders as full-time employees, the company is seeing healthy growth. It was selected for a $1.1 million award from the National Institutes of Health through its Blueprint MedTech program. The award was funded by the National Institute of Neurological Disorders and Stroke. The funding furthers NeuraStasis’ work for two years, and supports product development for work on acute stroke and for another product that will aid in emergency situations.

Gill says that he believes “Houston has been tailor-made for medical healthcare-focused innovation.”

NeuraStasis, he continues, has benefited greatly from its advisors and mentors from throughout the TMC, as well as the engineering talent from Rice, University of Houston and Texas A&M. And the entrepreneur says that he hopes that Houston will benefit as much from NeuraStasis’ technology as the company has from its hometown.

“I know that there are people within the community that could benefit from our device,” he says.