* Credit Suisse flags Q1 pre-tax loss, 4.4 bln Sfr Archegos hit

* Bank launches two separate investigations into recent troubles

* Replaces head of risk and compliance, investment bank executive

* Dividend slashed by two-thirds as bank halts buybacks

ZURICH, April 6 (Reuters) - Credit Suisse said on Tuesday it will take a 4.4 billion Swiss franc ($4.7 billion) hit from dealings with Archegos Capital Management, prompting it to overhaul the leadership of its investment bank and risk divisions.

The scandal-hit bank now expects to post a loss for the first quarter of around 900 million Swiss francs. It is also suspending its share buyback plans and cutting its dividend by two thirds.

Switzerland's No. 2 bank, which has dumped over $2 billion worth of stock to end exposure to the New York investment fund run by former Tiger Asia manager Bill Hwang, said Chief Risk and Compliance Officer Lara Warner and investment banking head Brian Chin were stepping down following the losses.

The Archegos hit eclipses the bank's 2.7 billion Swiss franc net profit last year, with questions over how its exposure to Hwang became so big remaining unanswered.

"The significant loss in our Prime Services business relating to the failure of a US-based hedge fund is unacceptable," Credit Suisse Chief Executive Thomas Gottstein said in a statement. "Serious lessons will be learned."

It is the second major scandal for Credit Suisse in just over a month after the collapse of Greensill Capital, with the bank's shares down by a quarter since March 1.

The bank's board has launched an investigation into the Archegos losses and also begun a probe into its $10 billion supply chain funds which invested in bonds issued by Greensill, which will be run by external parties.

Proposed bonuses for executive board members have been scrapped and outgoing chairman Urs Rohner, who has presided over the bank since 2011, will forgo his 1.5 million Swiss franc chair fee for the year.

Incoming chairman António Horta-Osório, currently CEO of Britain's Lloyds Bank, is being kept apprised of the investigations, which are being overseen by a "very senior member" of the board, a source familiar with the matter said.

Credit Suisse shares were down 0.5% at 1340 GMT with the bank saying the Archegos loss had overshadowed a "strong" start to the year by its investment banking and wealth management units.

"While the short-term impact seems less severe than feared, the full consequences from the reputational loss will only be visible over time," said Andreas Venditti, an analyst at Vontobel bank.

Credit Suisse said Christian Meissner, who ran investment banking at Bank of America before joining the Swiss lender last year, would be appointed chief of the investment bank from May 1. Joachim Oechslin will resume on an interim basis the role of chief risk officer, which he held until February 2019, while Thomas Grotzer will become interim global head of compliance.

Warner and Chin are paying the price for a year in which Credit Suisse's risk management protocols have come under harsh scrutiny. JPMorgan Chase & Co analysts estimate that combined losses from the Archegos and Greensill scandals could add up to $7.5 billion.

Australian Warner only took on the risk management and compliance role in August last year, having previously been group head of compliance and chief financial officer of the investment bank. Chin ran the bank's global markets unit between 2016 and 2020 before it was rolled into the investment bank.

Credit Suisse is in touch with Swiss, UK and U.S. regulators over the Archegos matter, the source said.

ARCHEGOS IMPLOSION

Archegos fell apart late last month when its debt-laden bets on stocks of certain media companies unravelled. Credit Suisse and other banks, which acted as Archegos' brokers, had to scramble to sell the shares they held as collateral and unwind the trades.

The episode, along with Greensill, adds to pressure on CEO Gottstein who has been trying to move Credit Suisse on from an earlier string of negative headlines spanning a spy scandal that ousted predecessor Tidjane Thiam to a $450 million write-down on a hedge fund investment.

Before Archegos the bank had been considering compensating investors in the Greensill funds according to four people familiar with the matter. Now, however, it is not expecting to book any material impact from Greensill in its first quarter earnings, according to the first source.

Credit Suisse said last month it will separate its asset management business from its wealth unit following the Greensill collapse and bring in former UBS executive Ulrich Koerner to lead the funds business.

"Obviously heads are rolling. After any sort of blow up there's always tighter control," said Jason Teh, chief investment officer at Vertium Asset Management in Sydney, adding the bank had lost a lot of money and its share price would struggle to rally.

While some banks were able to quickly offload collateral related to Archegos, including shares of ViacomCBS, Baidu Inc and Tencent Music Entertainment Group, Credit Suisse was still selling on Monday, a source familiar with the trading said.

However, the first source said Credit Suisse had now substantially reduced the vast bulk of its exposure to Archegos although some residual risk remained. Losses on the trades unwound on Monday will only be reflected in the bank's second quarter earnings, another source added.

(Reporting by Matt Scuffham in New York, Brenna Hughes Neghaiwi and John Revill in Zurich; Additional reporting by Tom Westbrook in Singapore; Writing by Rachel Armstrong Editing by Ira Iosebashvili, Edwina Gibbs, Kirsten Donovan)