Unbuttoned
By VANESSA FRIEDMAN

On the second floor of a classic cast-iron building in SoHo, just above the madding crowd, there is an airy loft, all cool cream tones and Pierre Paulin chairs, oversize art books and Henri Cartier-Bresson prints. Plus, along one wall is a rail of discreet white and black and marinière striped linen and silk, cotton and denim; culottes, shirtdresses, tunics and cashmeres. With price tags attached.

That’s because this isn’t actually an apartment at all. It’s an experiment, and that rail is Stage Three of a long-term plan to do what has never really been done before in American fashion: create a conglomerate of brands all born, if not permanently housed, under one roof.

The experiment is being conducted by Adam Pritzker, a positive-thinking spritelike 31-year-old scion of the billionaire Hyatt hotel family, and Vanessa Traina, the famously chic 31-year-old daughter of the romance novelist Danielle Steel and stylist/consultant/BFF of designers like Joseph Altuzarra and Alexander Wang.

It started in 2013, when Mr. Pritzker founded Assembled Brands. The next year they introduced an e-commerce site called The Line with a group of products “curated” by Ms. Traina, executive creative director. They opened a showroom in New York (The Apartment by The Line) and, after that, one in Los Angeles, with the products posed to look as if in a private house.

Peppered among those products was a new brand, Protagonist, an accessible luxury collection marked by its elegant discretion and owned by Assembled Brands, as well as Tenfold, an Assembled Brands homewares collection that recently expanded into T-shirts. Next week they are introducing their third line, Khaite.

Three being fashion’s magic number: the one that represents critical mass, trend or otherwise.

Khaite, designed by Catherine Holstein, late of Gap, is an advanced contemporary collection that looks kind of like a Scandinavian version of Tory Burch, with a quietly sybaritic windswept mood.

Like Protagonist, now stocked in 40 other boutiques including Net-a-Porter, it will initially be sold only at The Line, and then wholesale to the wider market.

There is talk of starting a men’s wear brand and a children’s wear brand, all part of what Ms. Traina calls “a distinct vision focused on defining a new kind of American sportswear that is less about trend and more about lifestyle.” Also about “sourcing the greatest new talent and providing the infrastructure for it to thrive.”

It all sounds logical enough. Except it has never worked before.

One of the perennial breast-beating questions in fashion – along with why women compulsively wear shoes that often seem more like instruments of torture, and why drop-crotch pants keep making a comeback even though everyone hates them — is why no conglomerate has arisen to rival the French behemoths Moët Hennessey Louis Vuitton (owner of Vuitton, Givenchy, Céline, Pucci and Fendi, among others) and Kering (Gucci, Yves Saint Laurent, Bottega Veneta, Stella McCartney, etc.), or the Swiss watch and jewelry giant Richemont (Cartier, Van Cleef & Arpels, Jaeger-LeCoultre, Vacheron Constantin, and so on — plus a few clothing names like Chloé, Dunhill, Alaïa, Shanghai Tang).

Labelux — which was created in 2007 by the Reimann family, the German owners of JAB Holdings (which also owns Coty and a number of coffee brands) — once owned Jimmy Choo, Bally, Belstaff, Zagliani, Solange Azagury-Partridge and Derek Lam. But they have faltered, with the group selling the last two brands back to their founders, putting Zagliani on ice, and renaming the subsidiary JAB Luxury. There are other examples.

In Italy, Only the Brave is currently making a stab at it (Maison Margiela, Marni, Viktor & Rolf, Diesel), and Tod’s owns Hogan, Roger Vivier and Fay (and Tod’s owner, Diego Della Valle, owns Schiaparelli). But they have nothing like the scale of LVMH and Kering. Which may be why, when LVMH swooped in and bought up Bulgari in 2011 and Loro Piana in 2013, it caused agony and soul-searching in Rome and Milan along the lines of, “Why can’t we keep our own brands in our own hands?”

This is also a question that comes up a lot in the United States, where name brands such as Marc Jacobs and Donna Karan are likewise owned by LVMH, and the only group even close to the European model is PVH, which owns Calvin Klein and Tommy Hilfiger (plus a lot of more mass-market names like Speedo and Izod).

Andrew Rosen, who founded Theory and later acquired Helmut Lang, was once credited by Anna Wintour with building “an American equivalent” of LVMH. But his company is now owned by Fast Retailing, the Japanese-based parent of Uniqlo, and while he has personal investments in Rag & Bone, Proenza Schouler and Alice & Olivia, they are minority stakes.

In 2000, to great fanfare, a group called Pegasus announced that it was going to be the American LVMH, and bought Miguel Adrover, Daryl K., Pamela Dennis, Judith Leiber and Angela Amiri, only to close or shed most of those lines by 2001, and rechristen itself the Leiber Group.

All of which raises the question: What do Mr. Pritzker and Ms. Traina think they know that all of these other fashion insiders did not?

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Two reasons most often given for the lack of an American group are absence of available heritage brands on which to build, and timing. When LVMH and Kering nee PPR were formed (in 1987 and 1999, the latter at the time being called the Gucci Group, and owned by PPR), most European brands were relatively local, family run businesses with big names, ripe for the acquisition. Now fashion is a giant global concern, and the financial outlay required to build these kinds of groups is exponentially greater.

Which is partly why Assembled Brands is doing none of the above. It is not interested in established brands but rather in making its own, an attitude that nods to the American mythology that mitigates against preservation in favor of creation; that values the idea of invention more than the idea of saving what was.

Its back-room synergies are not in capital-intensive areas like real estate, with its fixed costs, but rather in technology, with its related access to consumer data and e-commerce. And its ambitions begin at an entirely different place from the groups that went before.

Unlike François-Henri Pinault, the chief executive of Kering, who often talks about buying medium-size companies (with revenue between $50 and $100 million) and building them up, or LVMH, which spent $2.6 billion on Loro Piana, Mr. Pritzker dreams of expanding via a network of services for brands making around $1 million to $2 million a year in revenue.

He aims to use his experience and his own brands, started from scratch and shaped by Ms. Traina, to create an ecosystem with tentacles that provide services (financial, logistic, digital) to a host of independent emerging talent, so that the connected whole adds up to more than the sum of its parts.

As a result, one brand “doesn’t need to be a breakaway success to make the whole thing work,” Mr. Pritzker said.

“Not everyone wants to open 25 stores in five years,” he said. On the other hand, he is aiming at growth of 50 percent to 200 percent (“we cap it at 200 percent,” he said), with 50 percent to 60 percent margins, for his brands.

It’s a provocative theory: That you can build a big fashion business on the willingness to go small. Whether it works remains to be seen. But in any case, it’s a new line.