The company's HAMMR device is designed to produce therapeutic proteins inside the human body around the clock. Photo courtesy Rice University

Rice University’s biotech venture studio RBL LLC has launched a new “living pharmacy” company, Duracyte, designed to make cancer treatment easier on patients.

Backed by an up to $45 million Advanced Research Projects Agency for Health (ARPA-H) award, Duracyte aims to commercialize implantable biohybrid pharmacy devices that are designed to produce therapeutic proteins inside the human body around the clock, replacing the need for regular injections and infusions for some cancer patients.

The company’s main platform is its Hybrid Advanced Molecular Manufacturing Regulator (HAMMR), a rechargeable, implantable device that can sense biological signals, monitor tumor environments and adjust therapeutic output in real time. HAMMR has wireless communication capabilities, which allow patients and clinicians to remotely monitor results through an app every five minutes and make changes to treatment plans without a hosptial visit. Additionally, the device can generate its own oxygen supply, which is key for the therapeutic cells’ survival.

“Biologic medicines such as monoclonal antibodies, cytokines and metabolic regulators already account for a significant share of modern therapeutics, but the way we deliver them today often requires frequent injections or infusions that can be demanding for patients and lead to inconsistent drug levels,” Daniel Anderson, MIT professor and co-founder of Duracyte, said in a news release. “Our vision is to enable a continuous, stable therapy by producing these medicines directly inside the body, which could improve treatment consistency, reduce side effects and ultimately transform how biologic therapies are delivered across many diseases.”

Duracyte’s first clinical trial is slated to begin by the end of 2026 and will focus on recurrent ovarian cancer. The Phase I study will build upon existing work on encapsulated cytokine pharmacy technology, and the company hopes that within a few years this treatment can reach clinical application.

The development of Duracyte is supported by ARPA-H's Targeted Hybrid Oncotherapeutic Regulation (THOR) project, which supports a multidisciplinary research consortium co-led by Omid Veiseh, a professor of bioengineering at Rice. The consortium also includes others at Rice, The University of Texas MD Anderson Cancer Center, Stanford University, Carnegie Mellon University, Northwestern University and the University of Houston, plus industry collaborators like Chicago-based CellTrans.

“What we are building is the culmination of years of progress in cell engineering, biomaterials and implantable device technology,” Veiseh added in the release. “By combining these advances with real-time sensing and adaptive drug delivery, we are working with the support of RBL to create a true ‘living pharmacy’ that can deliver continuous, precisely controlled biologic therapies and fundamentally change how these treatments reach patients.”

RBL launched in 2024 and is based out of Houston’s Texas Medical Center Helix Park. Duracyte is the third company launched by RBL, including Sentinel BioTherapeutics, a clinical-stage immunotherapy company developing localized cytokine therapies for solid tumors, and SteerBio, a regenerative medicine company targeting lymphedema.

“Duracyte exemplifies the kind of breakthrough that Houston’s ecosystem is built to produce,” Paul Wotton, managing partner of RBL LLC and co-founder of Duracyte, added in the release. “With world-class clinical infrastructure, exceptional engineering talent and initiatives like the Texas Biotech Task Force driving alignment across industry, investment and talent, this region is uniquely positioned to move the most ambitious ideas in medicine from concept to patient, faster than anywhere else.”

MD Anderson is teaming up with TOPPAN Holdings on cutting-edge organoid tech to help match cancer patients with the most effective treatments. Photo via Getty Images.

MD Anderson launches $10M collaboration to advance personalized cancer treatment tech

fighting cancer

The University of Texas MD Anderson Cancer Center and Japan’s TOPPAN Holdings Inc. have announced a strategic collaboration to co-develop TOPPAN Holdings’ 3D cell culture, or organoid, technology known as invivoid.

The technology will be used as a tool for personalized cancer treatments and drug screening efforts, according to a release from MD Anderson. TOPPAN has committed $10 million over five years to advance the joint research activities.

“The strategic alliance with MD Anderson paves a promising path toward personalized cancer medicine," Hiroshi Asada, head of the Business Innovation Center at TOPPAN Holdings, said in a news release.

Invivoid is capable of establishing organoid models directly from patient biopsies or other tissues in a way that is faster and more efficient. Researchers may be able to test a variety of potential treatments in the laboratory to understand which approach may work best for the patient, if validated clinically.

“Organoids allow us to model the three-dimensional complexity of human cancers in the lab, thus allowing us to engineer a powerful translational engine—one that could not only predict how patients will respond to therapy before treatment begins but also could help to reimagine how we discover and validate next-generation therapies," Dr. Donna Hansel, division head of pathology and laboratory medicine at MD Anderson, added in the news release. “Through this collaboration, we hope to make meaningful progress in modeling cancer biology for therapeutic innovation.”

The collaboration will build upon preclinical research previously conducted by MD Anderson and TOPPAN. The organizations will work collaboratively to obtain College of American Pathologists (CAP) and Clinical Laboratory Improvement Amendments (CLIA) certifications for the technology, which demonstrate a commitment to high-quality patient care. Once the certifications are obtained, they plan to conduct observational clinical studies and then prospective clinical studies.

“We believe our proprietary invivoid 3D cell culture technology, by enabling the rapid establishment of organoid models directly from patient biopsies, has strong potential to help identify more effective treatment options and reduce the likelihood of unnecessary therapies,” Asada added in the release. “Through collaboration on CAP/CLIA certification and clinical validation, we aim to bring this innovation closer to real-world patient care and contribute meaningfully to the advancement of cancer medicine."

Sentinel BioTherapeutics is developing cytokine interleukin-2 (IL-2) capsules to fight many solid tumors. Photo via Getty Images.

New Houston biotech co. developing capsules for hard-to-treat tumors

biotech breakthroughs

Houston company Sentinel BioTherapeutics has made promising headway in cancer immunotherapy for patients who don’t respond positively to more traditional treatments. New biotech venture creation studio RBL LLC (pronounced “rebel”) recently debuted the company at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago.

Rima Chakrabarti is a neurologist by training. Though she says she’s “passionate about treating the brain,” her greatest fervor currently lies in leading Sentinel as its CEO. Sentinel is RBL’s first clinical venture, and Chakrabarti also serves as cofounder and managing partner of the venture studio.

The team sees an opportunity to use cytokine interleukin-2 (IL-2) capsules to fight many solid tumors for which immunotherapy hasn't been effective in the past. “We plan to develop a pipeline of drugs that way,” Chakrabarti says.

This may all sound brand-new, but Sentinel’s research goes back years to the work of Omid Veiseh, director of the Rice Biotechnology Launch Pad (RBLP). Through another, now-defunct company called Avenge Bio, Veiseh and Paul Wotton — also with RBLP and now RBL’s CEO and chairman of Sentinel — invested close to $45 million in capital toward their promising discovery.

From preclinical data on studies in mice, Avenge was able to manufacture its platform focused on ovarian cancer treatments and test it on 14 human patients. “That's essentially opened the door to understanding the clinical efficacy of this drug as well as it's brought this to the attention of the FDA, such that now we're able to continue that conversation,” says Chakrabarti. She emphasizes the point that Avenge’s demise was not due to the science, but to the company's unsuccessful outsourcing to a Massachusetts management team.

“They hadn't analyzed a lot of the data that we got access to upon the acquisition,” explains Chakrabarti. “When we analyzed the data, we saw this dose-dependent immune activation, very specific upregulation of checkpoints on T cells. We came to understand how effective this agent could be as an immune priming agent in a way that Avenge Bio hadn't been developing this drug.”

Chakrabarti says that Sentinel’s phase II trials are coming soon. They’ll continue their previous work with ovarian cancer, but Chakrabarti says that she also believes that the IL-2 capsules will be effective in the treatment of endometrial cancer. There’s also potential for people with other cancers located in the peritoneal cavity, such as colorectal cancer, gastrointestinal cancer and even primary peritoneal carcinomatosis.

“We're delivering these capsules into the peritoneal cavity and seeing both the safety as well as the immune activation,” Chakrabarti says. “We're seeing that up-regulation of the checkpoint that I mentioned. We're seeing a strong safety signal. This drug was very well-tolerated by patients where IL-2 has always had a challenge in being a well-tolerated drug.”

When phase II will take place is up to the success of Sentinel’s fundraising push. What we do know is that it will be led by Amir Jazaeri at MD Anderson Cancer Center. Part of the goal this summer is also to create an automated cell manufacturing process and prove that Sentinel can store its product long-term.

“This isn’t just another cell therapy,” Chakrabarti says.

"Sentinel's cytokine factory platform is the breakthrough technology that we believe has the potential to define the next era of cancer treatment," adds Wotton.

Xiaoyu Yang, a graduate student at Rice, is the lead author on a study published in the journal Science on smart cell design. Photo by Jeff Fitlow/ Courtesy Rice University

Rice research breakthrough paves the way for advanced disease therapies

study up

Bioengineers at Rice University have developed a “new construction kit” for building custom sense-and-respond circuits in human cells, representing a major breakthrough in the field of synthetic biology, which could "revolutionize" autoimmune disease and cancer therapeutics.

In a study published in the journal Science, the team focused on phosphorylation, a cellular process in the body in which a phosphate group is added to a protein, signaling a response. In multicellular organisms, phosphorylation-based signaling can involve a multistage, or a cascading-like effect. Rice’s team set out to show that each cycle in a cascade can be treated as an elementary unit, meaning that they can be reassembled in new configurations to form entirely novel pathways linking cellular inputs and outputs.

Previous research on using phosphorylation-based signaling for therapeutic purposes has focused on re-engineering pathways.

“This opens up the signaling circuit design space dramatically,” Caleb Bashor, assistant professor of bioengineering and biosciences and corresponding author on the study, said in a news release. “It turns out, phosphorylation cycles are not just interconnected but interconnectable … Our design strategy enabled us to engineer synthetic phosphorylation circuits that are not only highly tunable but that can also function in parallel with cells’ own processes without impacting their viability or growth rate.”

Bashor is the deputy director for the Rice Synthetic Biology Institute, which launched last year.

The Rice lab's sense-and-respond cellular circuit design is also innovative because phosphorylation occurs rapidly. Thus, the new circuits could potentially be programmed to respond to physiological events in minutes, compared to other methods, which take hours to activate.

Rice’s team successfully tested the circuits for sensitivity and their ability to respond to external signals, such as inflammatory issues. The researchers then used the framework to engineer a cellular circuit that can detect certain factors, control autoimmune flare-ups and reduce immunotherapy-associated toxicity.

“This work brings us a whole lot closer to being able to build ‘smart cells’ that can detect signs of disease and immediately release customizable treatments in response,” Xiaoyu Yang, a graduate student in the Systems, Synthetic and Physical Biology Ph.D. program at Rice who is the lead author on the study, said in a news release.

Ajo-Franklin, a professor of biosciences, bioengineering, chemical and biomolecular engineering and a Cancer Prevention and Research Institute of Texas Scholar, added “the Bashor lab’s work vaults us forward to a new frontier — controlling mammalian cells’ immediate response to change.”


Cellenkos Therapeutics has completed promising Phase 1b testing of its Treg cell therapy, CK0804, in the fight against myelofibrosis. Photo via Getty Images

Houston biotech company tests hard-to-fight cancer therapeutics

fighting cancer

A Houston-based, female-founded biotech company has developed a treatment that could prove to be an effective therapy for a rare blood cancer.

Cellenkos Therapeutics has completed promising Phase 1b testing of its Treg cell therapy, CK0804, in the fight against myelofibrosis. According to a news release from the Cellenkos team, the use of its cord-blood-derived therapeutics could signal a paradigm shift for the treatment of this hard-to-fight cancer.

Cellenkos was founded by MD Anderson Cancer Center physician and professor Simrit Parmar. Her research at the hospital displayed the ability of a unique subset of T cells’ capability to home in on a patient’s bone marrow, restoring immune balance, and potentially halting disease progression.

Myelofibrosis has long been treated primarily with JAK (Janus Kinase) inhibitors, medications that help to block inflammatory enzymes. They work by suppressing the immune response to the blood cancer, but don’t slow the progression of the malady. And they’re not effective for every patient.

“There is a significant need for new therapeutic options for patients living with myelofibrosis who have suboptimal responses to approved JAK inhibitors,” Parmar says. “We are greatly encouraged by the safety profile and early signs of efficacy observed in this patient cohort and look forward to continuing our evaluation of the clinical potential of CK0804 in our planned expansion cohort.”

The expansion cohort is currently enrolling patients with myelofibrosis. What exactly are sufferers dealing with? Myelofibrosis is a chronic disease that causes bone marrow to form scar tissue. This makes it difficult for the body to produce normal blood cells, leaving patients with fatigue, spleen enlargement and night sweats.

Myelofibrosis is rare, with just 16,000 to 18,500 people affected in the United States. But for patients who don’t respond well to JAKs, the prognosis could mean a shorter span than the six-year median survival rate outlined for the disease by Cleveland Clinic.

Helping myelofibrosis patients to thrive isn’t the only goal for Cellenkos right now.

The company seeks to aid people with rare conditions, particularly inflammatory and autoimmune disorders, with the use of CK0804, but also other candidates including one known as CK0801. The latter drug has shown promising efficacy in aplastic anemia, including transfusion independence in treated patients.

The company closed its $15 million series A round led by BVCF Management, based in Shanghai, in 2021. Read more here.

March Biosciences' oversubscribed raise brought in $28.4 million of financing with Mission BioCapital and 4BIO Capital leading the pack of investors. Photo via Getty Images

Clinical-stage Houston cell therapy company closes $28.4M oversubscribed series A

cha-ching

An emerging biotech company in Houston has closed its series A with outsized success.

March Biosciences' oversubscribed raise brought in $28.4 million of financing with Mission BioCapital and 4BIO Capital leading the pack of investors. The company has now raised more than $51 million in total.

Last year, March Biosciences announced its strategic alliance with CTMC (Cell Therapy Manufacturing Center), a joint venture between MD Anderson Cancer Center and National Resilience. CEO Sarah Hein met her co-founder, Max Mamonkin, at the TMC Accelerator for Cancer Therapeutics. Along with fellow co-founder Malcolm Brenner, March Biosciences launched from the Center for Cell and Gene Therapy (Baylor College of Medicine, Houston Methodist Hospital and Texas Children’s Hospital). Its goal is to fight cancers that have been unresponsive to existing immunotherapies using its lead asset, MB-105.

An autologous CD5-targeted CAR-T cell therapy, MB-105 is currently in phase-1 trials in patients with refractory T-cell lymphoma and leukemia. The treatment is showing signs of being both safe and effective, meriting a phase-2 trial that will begin early next year. The funds raised from the series A will help to finance the Phase 2 clinical development of MB-105 to expand on the existing data with optimized manufacturing processes.

“This oversubscribed financing enables us to advance our first-in-class CAR-T therapy, MB-105, into a Phase 2 trial for T-cell lymphoma – an indication with an exceptionally poor prognosis and few treatment options,” says Hein. “With the support and confidence of our investors, we are not only advancing our lead program but also expanding our pipeline, underscoring our commitment to delivering best-in-class therapies to patients that can change the treatment paradigm for these challenging cancers.”

But that’s not the only exciting news that Hein and her associates have to report. March Biosciences has recently partnered with cell therapy venture studio, Volnay Therapeutics. Led by highly experienced cell therapy development veterans, the March Biosciences team will work to develop a scalable manufacturing process for MB-105 that will lead to commercialization. Volnay co-founder and CEO Stefan Wildt, who held key R&D leadership positions in cell and gene therapy units at Novartis and Takeda, has also joined the board of March Biosciences. The board of directors is also welcoming Cassidy Blundell of Mission BioCapital and Owen Smith of 4BIO Capital.

“The team at March Biosciences is leveraging powerful science and promising clinical data to tackle cancers with significant unmet need,” says Blundell, a partner at Mission BioCapital. “We're excited to support their journey and believe their focused approach with MB-105 could lead to significant breakthroughs in the CAR-T space.”

The Houston-born company, which is a finalist for the 2024 Houston Innovation Awards, continues to accelerate quickly, in part thanks to its home base. After all, existing local investors like TMC Venture Fund also participated in the new raise. As Hein said last year, “Working with partners here in Houston, we have all the pieces and the community rises to the occasion to support you.”

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Houston-based Fervo Energy bumps up IPO target to $1.82 billion

IPO update

Houston-based geothermal power company Fervo Energy is now eyeing an IPO that would raise $1.75 billion to $1.82 billion, up from the previous target of $1.33 billion.

In paperwork filed Monday, May 11 with the U.S. Securities and Exchange Commission, Fervo says it plans to sell 70 million shares of Class A common stock at $25 to $26 per share.

In addition, Fervo expects to grant underwriters 30-day options to buy up to 8.33 million additional shares of Class A common stock. This could raise nearly $200 million.

When it announced the IPO on May 4, Fervo aimed to sell 55.56 million shares at $21 to $24 per share, which would have raised $1.17 billion to $1.33 billion. The initial valuation target was $6.5 billion.

A date for the IPO hasn’t been scheduled. Fervo’s stock will be listed on Nasdaq under the ticker symbol FRVO.

Fervo, founded in 2017, has attracted about $1.5 billion in funding from investors such as Bill Gates-founded Breakthrough Energy Ventures, Google, Mitsubishi Heavy Industries, Devon Energy (which is moving its headquarters to Houston), Tesla co-founder JB Straubel, CalSTRS, Liberty Mutual Investments, AllianceBernstein, JPMorgan, Bank of America and Sumitomo Mitsui Trust Bank.

Fervo’s marquee project is Cape Station in Beaver County, Utah, the world’s largest EGS (enhanced geothermal system) project. The first phase will deliver 100 megawatts of baseload clean power, with the second phase adding another 400 megawatts. The site can accommodate 2 gigawatts of geothermal energy. Fervo holds more than 595,000 leased acres for potential expansion.

Cape Station has secured power purchase agreements for the entire 500-megawatt capacity. Customers include Houston-based Shell Energy North America and Southern California Edison.

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This article originally appeared on our sister site, EnergyCapitalHTX.com.

Texas university's new flight academy opens at Houston Spaceport

cleared for takeoff

The vehicles may not have “student driver” stickers on them, but Texas Southern University has moved a dozen planes into its new training facility at the Houston Spaceport, opening the way for student flyers to use the facility.

TSU previously reached a deal with Houston Airports and the City of Houston in 2023 to house its prospective Flight Academy at Ellington Field. At the time, TSU had a small fleet of nine planes for student use, but a $5.5 million investment from the city greatly expanded the space available.

The Flight Academy includes a 20,000-square-foot hangar that serves as a TSU satellite campus. The school now has a fleet of 12 Cirrus SR20 aircraft that were acquired last year through state and alumni funding. An additional 4,500 square feet is used as classroom and office space. An 8,000-gallon fuel tank will support flight training operations.

TSU first launched its Aviation Science Management program in 1986 and added a professional pilot program in 2016. The school is now part of the United Airlines pipeline program and has also forged relationships with Delta and Southwest.

“I want to commend Texas Southern University and Houston Airports for their leadership and partnership in advancing aviation education right here in our city,” Houston City Councilwoman Dr. Carolyn Evans-Shabazz in a press release.

“It connects our students to high-paying, high-demand careers in aviation and aerospace. This is how we grow a city in the right way—by investing in workforce development, aligning education with industry and making sure our residents are prepared to lead in the industries of tomorrow. Houston is already a global leader in aerospace and projects like this strengthen that position even further, especially here at Ellington, where innovation and opportunity continue to take flight.”

The City of Houston signed an agreement to continue funding the academy for five years.

Amazon launches ultrafast, 30-minute delivery service across Houston

Amazon Now

More than 20 years after it redefined fast shipping, Amazon is preparing to raise the bar on consumer expectations again by offering to fulfill customers' most urgent product needs in Houston and other parts of the world in a half-hour or less for an extra fee.

The company, which revolutionized online shopping in 2005 with two-day deliveries for Prime members, is rapidly opening small order-processing hubs in dozens of U.S. and foreign cities to cater to shoppers who can't or don't want to wait for cough medicine to relieve flu symptoms or tomatoes for tonight's dinner salad.

The ultrafast service, called Amazon Now, first launched in India last June. Amazon says 30-minute deliveries now are also available in urban areas of the United States, Brazil, Mexico, Japan, the United Arab Emirates, the United Kingdom.

The mini-warehouses devoted to Amazon Now are about the size of a CVS drugstore. They stock about 3,500 products for expedited delivery, including beer, diapers, pet food, meat, nonprescription medications, playing cards and cellphone charging cables.

“We know that customers love speed and always have,” Beryl Tomay, Amazon’s head of transportation, told The Associated Press on Monday. “What we see customers doing, when we offer faster speeds, are they purchase more from Amazon. And Amazon becomes more top of mind for that or other types of items as well.”

In the U.S., the company first tested Amazon Now in Seattle, the home of its headquarters, and in Philadelphia. Most residents of the Dallas-Fort Worth area and Atlanta now have access as well. The service is also live in Dallas-Fort Worth, Denver, Minneapolis, Phoenix, Oklahoma City, Orlando, and dozens of other cities, Amazon said, with New York City and others expected by year-end.

The service charges for Amazon Now start at $3.99 for Prime members, who pay an annual fee of $139, and $13.99 for non-members. A $1.99 small basket fee applies to orders under $15, Amazon said.

The company's bet on a need for speed also comes as some consumers are rebelling against rushed deliveries as they weigh the potential impact on the environment and the workers tasked with preparing orders at a rapid rate.

Amazon’s approach
A relentless focus on speed helped Amazon build a logistics and e-commerce empire. After it made two days the new delivery time normal, Amazon moved into one-day and same-day deliveries for its Prime members. This spring, the company began making 90,000 products available in one hour or three hours at an extra cost.

The scaled down and sped up microhubs that are designed to handle 30-minute orders represent another step in Amazon's pursuit.

Only a handful of people prepare orders from aisles of shelves in the 5,000- to 10,000-square-foot facilities, unlike the sprawling fulfillment centers storing millions of items where Amazon employs a mix of human workers and robotics to pick and pack orders.

Amazon tailors the product inventory to each location and uses artificial intelligence and other technology to analyze what customers buy, as well as when and how often. The most popular U.S. purchases so far include soap, toothpaste, mouthwash, toilet plungers, bananas, limes and wireless earbuds, Amazon said.

The competition
Amazon’s attempt to up the instant gratification ante provides direct competition to on-demand food delivery platforms like Instacart, Uber Eats, DoorDash and Grubhub, which don't have the scale of the e-commerce titan, according to independent retail analyst Bruce Winder.

“What Amazon brings is their prowess in supply chain,” Winder said.

These smaller companies said they don't see Amazon as a threat, though, citing the hundreds of thousands of items they are able to deliver to users' doorsteps by partnering with various merchants and restaurants.

“DoorDash has a mission to empower grocers and retailers and augment their existing footprint, not to replace them,” DoorDash spokesperson Ali Musa said in an emailed statement. “We win only when they win, which is how we can offer over half a million grocery and retail items in under an hour across the country.”

Amazon also is in a race with Walmart to become the retailer that reliably gets orders to online shoppers in under an hour.

For an additional $10 on top of standard delivery charges, shoppers can place Walmart Express Delivery orders from among more than 100,000 products that are guaranteed to arrive in an hour. Many customers, however, are receiving the items under 30 minutes, Walmart CEO John Furner told analysts in February.

Domino's cautionary tale
Companies have promised deliveries in 30 minutes or less before, but the landscape also is littered with failed attempts to break the speed barrier.

The COVID-19 pandemic produced a flurry of companies that promised 10- to 15-minute grocery deliveries from microwarehouses in dense neighborhoods, according to Sucharita Kodali, an analyst at market research firm Forrester Research.

But soaring operating costs, low customer loyalty and the drying up of investor money ultimately caused most to fail before the pandemic was over, analysts said.

Domino’s in 1984 pushed a guarantee that customers would receive their pizzas for free if they weren't delivered in under a half-hour. The company amended the “30 minutes or it’s free” policy after two years, providing only a $3 discount for late deliveries.

The promotion helped Domino’s win market share, but it ended up tarnishing the company's reputation. It dropped the guarantee in December 1993 after a string of crashes and lawsuits involving drivers racing to meet the deadline.

Brad Jashinsky, a retail analyst at information technology research and consulting firm Gartner, said he thinks Amazon should take the pizza chain's experience as a cautionary tale.

“You get in trouble when you start overpromising something like that,” he said.

Amazon won't be making any time guarantees and instead plans to keep customers who chose the 30-minute delivery option updated on the progress of their orders, Tomay said.

“There's no rushing either in our building workers or the gig workers,” she said.

Taking it slow
Kodali thinks Amazon will need a lot of people placing orders around the same time from the same or adjacent apartment buildings for the 30-minute service to be cost-effective.

Consumers may appreciate rapid receipt of products like toilet paper and batteries, but retailers and logistics experts said they also see some online shoppers, especially members of Generation Z, choosing no-rush shipping for products they don't need in a hurry.

Amazon for several years has invited customers to skip one- or two-day delivery and to receive their orders on the same day in as few parcels as possible. Consolidating orders into fewer packages by electing to have them delivered at the same time cuts down on boxes, shipping envelopes and fuel use, analysts said.

“The millennials who came to age in an era that was on fast delivery came to expect it de facto, whereas ... Gen Z is more accepting of a slower speed than previous generations before them,” said Darby Meegan, a general manager at Flexport, a supply chain and logistics company that fulfills orders for thousands of online merchants.

Still, Amazon executives have cited positive early results for Amazon Now in India, where they said Prime members tripled their requests for 30-minute deliveries once they started using the service.

Amazon Now also is attracting more repeat American customers, Tomay said.

“It’s in early days and time will tell,” she said. “I think that it will be interesting to see how it evolves.”